Are there male Nymphs on Roman mythology?

Answer 1

No; nymphs are strictly meant to be FEMALE nature spirits. This does not mean that in Greek myth there are not male nature spirits, only that the females are called nymphs.

MALE nature spirits are called satyrs.

Answer 2

No, they were depicted as young maidens. However, there are a few exceptions, such as Fontus.

Answer 3

No, and for a simple reason: because nymphs are female minor goddesses of nature.

The male minor gods of nature were called Satyroi- and the Potamoi the river-gods.