Pruning Rugosa Roses?

I know that all I have to do is trim my Rugosa Roses to keep them under control, but due to lack of time over the last 2 years I have a few areas that are out of control. Will a hard prune on these out of control branches create a problem for the whole plant and would it be better to prune now or can I leave it until after they bloom?

Hardiness Zone: 3b

By elaine from northern/central Ontario, Canada