After 16 years of MTB's- 5 years ago I went road. Bought a new basic OCR3 and it served me well. I bought the XS size frame and I am 5'6" with a 30" inseam. This is classed as a 49cm frame and although I did try the next size up- I preferred the fit of the XS. It was too small but it lasted me a year before my abilities outgrew the bike.
Raised the seatpost to the correct level and bought a riser stem to bring the bars up. That bike fitted me well although it was never really comfortable. It sdid its job though and got me into road riding at a cheap price. It got me over a few hilly rides- and a few century rides so it served its purpose.
Mind you-the next bike was the next size up- had far better components and fitted better. It also cost a fortune but still riding it and still doing the mountains and century rides although the next bike I bought was better for the mountains. Then there was the one for normal rides aswell so watch out- this bike game can become expensive.
I made the OCR fit and although it was one size too small- It did the job. And remember- all the first bike is there for is to tell you what the next bike will be--On type- fit- size and components.