Eroommate.com sounds much better then Iroommate.com imo.
Based on data from namebio (please find attached), I would estimate it something like USD 3000 - USD 10 000, or maybe even higher..it really depends on who the end user would be.
I just checked that Roommate.com redirects to Roommates.com which is fully developed successful business. So for anybody who wants to run something similar, Eroommate.com might be good option