Roman 2D 

This is a 3-suited hand with unspecified shortness. The pointrange can you decide yourself, but you shouldn't use it with more than a 4 points difference. Precicion use it as 11-15, and other popular range is 12-15, 17-20. 

If responder is weak he will bid a suit at a low level. Opener will pass with 4 card or correct with single. A jump is invitational and ask opener to correct if single.

Responder bids 2NT to ask for the short suit.
Opener may bid his single, but you can also use the a transfer bid, were opener bid the suit below his single. Then responder can bid openers single suit to ask for more information like strength, controls etc.