I'm kinda an expert on planting roses wrong, so I'm gonna pipe in here a little.
Transplanting a rose is uber easy. I wouldn't be toooooooooo hung up on the exact number of hours a day a plant gets sun. My front yard is north facing so gets less sun than some parts of my back yard - some parts fry all day, others are shaded until like noon, then get 2-3 hours before the trees / neighbors' houses get in the way. A rose will tell you if it's not happy by a couple of factors: size & blooms. I had, on the west side of my back yard, about 30 roses. They were all pretty spindly & not very robust and extremely stingy with blooms. Took me almost 2 years to figure it out.. they needed more sun as they'd only get hot hot noon - 3pm sun, then that was it. So I transplanted all the west side roses to the east side & they're much happier now. There are some roses that pretty close to my house in the front yard that don't get sun until about 10-1030 am, then get sun until about 2ish, then not much after that (and none at all after 3pm). Those roses are doing just fine.. big, bushy, & bloom way better than some of the ones in full all-day sun. So, your rose will tell you what it likes & what it doesn't. If it's getting less than 2-4 hours of sun, then yea, you'll probably need it. Also, the color of the leaves can help determine a lot about how a rose is doing. Leaves that are crisp, firm, & a nice healthy "green" (green is subjective in roses. Rose leaves range from a lighter "grass" green to a deep "leathery" green), then you're doing OK. If leaves are getting wilty & soft, kinda like lettuce left in the fridge too long, you're probably over-watering. Roses are thirsty, but they also don't like to drown and hate "wet feet" (standing water where their roots are). I would invest in a moisture stick (
https://www.amazon.com/dp/B005T4720I/). You can probably get one of those from a local nursery as I dunno if big boxes carry them. They're very handy when you have no idea what's going on 6-12" down below the surface of the ground.
Now for the transplanting part. First, figure out where you want the rose to go. Trust me, it'll save your back a LOT of pain to figure that out first rather than dig a hole, pop it in, then 2 weeks later, figure out that you hate it there. Lyn makes the great idea of putting a container where you'd think you'd want the rose to go. However, if you're anything like me, you won't see a container. So get something big & bright there.. a bird feeder, put some fake flowers in the container, put a kid's tricycle there, something. Something that's outta place & will catch your eye. Look at that spot for a week or two. Does it fit in your mind as to what your yard is gonna ultimately look like? If so, then dig your hole. If not, move it around. Figure it out. Envision what the end product of your yard is gonna look like. Don't expect your yard to look instantaneously like you see in your mind. It's taken me almost 5 years to get my front yard to what I saw it in my mind back in '08 and I'm STILL not finished with it! Gardening is a never-ending battle of wits, sore muscles, availability of what you're wanting, bugs, weeds, weather, and money (especially the last!). But when you finally get to that point, you'll be SO happy with what you have!!
Once you figure out exactly where you want your rose to go, go ahead & dig the hole. You'll want the hole at least 2x the size of the root ball. What I do is use the bucket that it came in as a guide if possible. I'm not saying dig a hole 4' deep by 4' wide. God no. I said root ball. About 50-80% of the stuff in the bucket is not root ball, but soil / junk the nursery puts in. So, for a 2gal rose, I'd dig a hole about 18" deep by at least 12" wide. If you can go 2x2, that'd be awesome, but not overly necessary. You don't have to worry about planting deep like I do (different zone, so the way I grow roses is a bit different than how you would). Once you have the hole dug, check out the soil. Try to determine what it is. You may want to amend it, you may not. If you do want to amend it, amend no more than 50% (that's the advice that we're given here in CO for strong root systems.. CA may be different) as you want the rose to grow natively & naturally in your soil & not rootcircle itself in the "good dirt". Also, talk to neighbors. See if you have gopher/vole/mole problems. I know that in a lot of areas in CA, they have gopher problems (just ask Zuzu how many roses she's lost to gophers!). If you do, you may want to invest in a gopher cage (a metal mesh "cage" that goes into the hole that you put the plant in so the gopher can't dig into the roots & eat them, killing the plant. Then go back to the other rose. Personally speaking, I'd do this late late afternoon / early evening. You don't wanna be digging in the heat of the day for health reasons AND it's (IMO) gentler on the plant. Spade around the rose (since it's freshly planted, should be super simple) and try to disturb as little soil as possible. Moving quickly, possibly with the rose still in the shovel, pop it into the new hole and backfill around the rose with the excess dirt, creating a little trench/moat around it. Go & fill the moat up with water (hose water should be OK, but if you have access to non-city water, that's much more preferred IMO. If you don't have access to non-hose / city water, what you can do is, a few days beforehand, fill a 5gal bucket w/water & put it out in the sun. The heat/sun will dissipate the chlorine / chloramine within 24 hours. Heavier metals such as copper / lead won't dissipate, but there's not a heck of a lot you can do w/o a RO system.), watching the water soak in. This will tell you were there was air pockets in the hole (the water will cause the dirt to collapse in those "caves", then you can fill in the holes created. Plus you can watch how fast / slow the water drains. You want it to drain at a moderate pace. Too fast means too much sand. Too slow = clay. Doesn't drain = rock. Give the rose a minimum of a gal of water.. try not to give more than 5gals as you don't wanna drown the poor thing. If you wanna add some kind of booster, ok. Personal choice. Sometimes I will, sometimes I won't (depends on how lazy I am to go into the garage to get some root stimulator). Me personally, I then put mulch around the base of the rose. This protects from the heat / sun and keeps moisture in the soil, plus, with my horrific soil, helps naturally amend it from clay crap into worm-filled dirt. But, again, this is personal choice. Then leave the rose alone. As mentioned before, do NOT be surprised or alarmed if the rose drops all it's leaves. Perfectly normal. I transplanted a 3 year old climber from next to my house where it got NO sun into an area that gets full sun for about 6 hours a day. Every leaf fell off & I thought for sure I killed it. I pruned it hard (cut off about 6-7' of the canes, leaving 3' canes) and left it alone, watering about once a week. Within about 2 weeks had full sets of leaves and about a month, actually got blooms! And that was surprising because this particular rose is an early spring bloomer and this was in the middle of July that she bloomed! You should also prune a little. This encourages new growth. Just a little.. not a buzz cut. Me personally, I'd cut off about 1/3 of the length of the canes and go from there.
Now that I've rambled on & on, I hope that some of this might be useful for your situation. And please, never be afraid to ask questions! The experts here are wonderful people and are always willing to help newbies like myself with growing pains!
