Roomies are a good concept to save the money and have an instant on board connection. If it wasn't for that extra money outpour to sail, I (as a single, which is fairly new to me) I would lean towards going solo for room freedom. The con is having no connection with anyone, which I find that is what I miss.
I have made an initial contact with a poster for a cruise share here on the east coast, but my booking fee is now almost $200 more than they paid and it's a higher catagory than I usually book. I had that thought about asking to pay the lower catagory fee to offset their cost of the cabin. It would help me and be cheaper for her.
So, that option could be possible if that's a choice for you. I'm sure I'm not the only one who wondered about this.