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.