I think if you must use a bagged mix, Schultz or MiracleGro are probably the best choices... however, I think your roses would be much happier planted in the appropriate Al's Mix.

You can find recipes for Al's Mix, and the information on why it's so healthy for plants, by reading thoroughly some of the articles written and posted by "tapla"... there are several very educational articles on soils and watering that should be required reading for every gardener!

I've posted the link below... give it a read, and then think about how you want to proceed with those roses! I hope this helps! I can tell you that what I have learned from reading Al's articles has helped my gardening skills improve immensely!

Here is a link that might be useful: Container Soils - Water Movement & Retention V