The short answer to your question is: No.
Automobile paint is very different from Rustoleum. Trying to apply it with a roller would just create a mess. While I'm not a professional 'body man', I've been repairing and painting my own cars for over 40 years.
The first thing I would do is go to a place like AutoZone or O'Reillys and try to find the color of your car in a spray can. Not all colors are available, but quite a few are. Find the color code on your car before you go, because that's the first thing the clerk will ask you. It should be on a little tag either in the glove box or under the hood. Since the bumper is already primered, all you would have to do is sand it lightly, clean the area thoroughly with clear water; then tape the margins and spray it. If you decide to do this, buy wet-or-dry sand paper in either 600 or 800 grit and use it wet. You should also use a sanding block behind it and let the area dry at least overnight before applying paint. The store employees should know what to sell you. You'll want to spray quite a few light coats and let them 'flash dry' between coats to get the color even and prevent runs.
If you can't find the paint in a spray can, your choices become much more limited because just having the paint mixed is a pretty expensive proposition. Then you would have to buy some other supplies (like reducer) and also have some way to apply it. There is a device made by a company called Pre-Val that allows you to spray automotive paint by attaching small canisters of compressed air, but then again, you're into quite a bit of expense.
My advice would be to simply live with it until you can have it repaired properly. And, I'd definitely either talk to your local Better Business Bureau or check out Angie's List before choosing another body shop!
I certainly hope you can resolve your problem and get your Toyota looking good again...
Dave B.