Kris, raised beds require more water. People put roses in raised beds either because they like the looks or because they have poor drainage.

Sandy soil conducts water easily and that is the first requirement of good drainage. The second requirement is that water at the root level has to have some place to go and that requirement will be satisfied by the proper location - on the upper parts of a sloping site, not at a low place in your yard.

The usual way sandy soils are amended is with organic matter and a standard way would be to add about 4 inches of compost over the entire bed and then plow it in to about the 12 inch level. This would take about 2 yards of compost for each of your beds. Backfilling a hole with Miracle Grow leaves most of the soil in your bed unamended and is likely to result in some serious settling of the soil in the coming year. It will also maximize any drainage problems you might have.

If you can get bulk quality compost delivered, or if you have a truck and can go get it, that is the best way. Thoroughly amending your entire beds with compost as Mike says will make your roses happy for many years to come.

I would leave at least 3' between the house and the rose. They get much bigger than you can ever imagine.