Thank you for the question.   Rugosa roses have very dense foliage that makes it difficult to see the plant structure so late winter to early spring, just as new leaf buds begin to swell, is the proper time to prune. Typically, this type of rose bush doesn't need much pruning, maybe only every 2-3 years to keep it performing well.  Next spring, remove one-third of the oldest stems -- or one out of every four or five -- at the base. When a rugosa is outgrowing its space, or you want to control the direction of its growth in years when you aren't renewing the plant, you can shorten the stems back to the next branch that is heading in the direction you prefer. These "heading" cuts are also made in late winter to early spring. Damaged or diseased canes can be removed anytime.

Here is more information:

Thank you for contacting Extension.