That is a great area to work with. I can picture more roses planted near the existing rose bushes.
A sign-up sheet at the church might be a good idea. Each person who wants to donate can sign up and give a donation for the plants you need to buy. But why stop there? Since you are willing to do the work, the congregations should be willing to kick in, each to their own ability. Some folks might donate an hour of sweat; others might donate money; others may only be able to make suggestions as to color and plant choice if they have no money to spare; some might just be nice enough to bring you lemonade and cookies and keep your spirits up while you do the work.
Make a list of all the materials for the project:
weed block fabric
soil amendments
slow-release fertilizer
mulch
plants; annuals, perennials, ground-cover, bulbs
etc.
