Remember that one big bag of potting soil will cover approximately 4 feet or more of ground. The depth should be at least 12'or 1 ft. Once the ground is tilled completely spread the potting soil evenly over the tilled surface with about 1 inch on top of the soil you just tilled. Then take your hoe or rot tiller and go back over the soil till it is well incorporated and the ground is a deep brown in color. Find a rose bush that has a lot of green on it.
Brown spots mean that there is very little live in it left.
If they also have started to bloom then check also to make sure that the blooms like something you would buy if you were picking out a rose for a loved one. Depending on your garden size the rose bushes have to be spread out about a half of a foot to a foot apart so don't go bananas buying roses only get as many as you think will fit in your garden. For example if you have a 4 foot garden by 4 foot garden you should buy 9 or 10 rose bushes that are in good health. Even if you have too many don't worry you can always follow the steps above to make you garden bigger. Also get you 2 buckets one for the roses and one for you to sit on.