What is the soil these roses are growing in like?
What will the weather be in March? Will the soil still be covered with snow then?
How much organic matter is in the soil?
How well does that soil drain?
What is the life in that soil like?
I would make compost with that manure and then apply the compost in the fall.

I agree with Kimmsr; if that goat manure is fresh, it should be composted before you put it on your roses. As for fertilizing, I do that right after I prune my roses around mid-april (when the forsythia in my neighbour's yard blooms - how luck am I to have one right there in front of me). Alfalfa, compost, or composted manure will get them off to a good start.
Judith