In original Precision, 1 was a natural opening bid. Hands lacking a 4-card that were unsuitable for an opening bid of 2 needed to go somewhere. Mini-Roman was the solution. This 2 opening bid shows:

11-15 HCP, 4 4 1 4 / 4 4 0 5

The big disadvantages of this opening bid is that the hand type is rare, and that it takes away the valuable 2 opening bid, which may be used for something else, like a Weak Two or Multi.

Responses to 2

2/ To play
2NT Strong asking bid
3 To play
3 Semi-solid suit, invitational