I live in South Florida. Every once in a while my mulch seems to wither away. I want to get my rose beds looking pretty again and want to put new mulch down. I use the no float kind, I think it is cypress. I'm trying to go strictly organic now but I have sprayed chemicals and use granules. Mostly Bayer 3 systemic. I'm assuming the present mulch has remnants of these chemicals. Should I remove this mulch before placing the new mulch or just put new mulch on top? How should I treat the dirt? Leave it as is or do you have a suggestion?

It is probably not possible to remove all the previously applied chemicals; they will degrade over time. I would be inclined to just add more of your favorite organic mulch. The old mulch will decompose becoming compost to improve your soil.

The chemicals actually disappear pretty fast in our hot, humid summers with heavy rain. What the plant has not already absorbed will be gone soon enough.

If you're going to put down fertilizer or soil amendments for your roses going into fall, I'd do that before putting down the new mulch though. You can't add enough compost and other amendments to our sandy soil! Alfalfa pellets (horse food) make a terrific soil amendment that also gives a boost of nitrogen. Roses love it, as do most other plants.