Hi, I am not too sure about that but I am sure Moongrowe and Bamboo advise that the sap is too high for certain shrubs and trees, not sure if this applies to roses though.

You don't mention where you are and what type of roses you plan on pruning.

Generally speaking I would say there is stil time to do it.

Have a read of this and see if it fits your situation;

http://www.thegardenersalmanac.co.uk/Data/Rose/Roses.htm

You can prune them now, even though its late, but it will mean later flowering. Note that climbers and bush roses should be pruned early March and ramblers in September.