I've never had room mates, other than gf's who lived with me or stayed the night, etc. That said, I keep exploring the idea of room mates. One of my rentals that I used to live in is ideal for it.
-Large rambler, with the other bedrooms on the other side of the house with their own bathroom. Two living rooms, one of which is a seperate living area that I can close the french doors to. The master bedroom has an in suite 3/4 bath, and a seperate living area with it's own fireplace, french doors, and a sliding glass door to the large deck (there's another fireplace in the other living room).
-I bought the house at the bottom of the market and got a killer interest rate with almost no money down. My mortgage payment is so small, that after principal and taxes, I'm paying LESS than $500 a month to live there, and $300 of that is taxes and insurance. I could get get $1,050 a month for the two rooms (one is slightly larger and has a walk in closet so I would charge $50 more than the other room) which would cover my post benefits house payment, utilities, internet and several hundred dollars worth of other expenses.
-The house has a large yard and I can legally have livestock (and did when I lived there) and garden my food for the most part.
-The house is walking distance to trains, buses, etc., and only a 30 minute drive to Seattle.
I'd still have other investments to live off of, including two dedicated rentals and some dividend stocks, but I can't help notice that with the right layout of a house, having a couple of room mates drastically helps on the path of FI. As seen in the case above, it basically pays my cost of housing, utilities, internet, cell phone, food, and a few other things. To the point that I'd only need $400 a month at the high end from my investments to pay for anything else.
Yes, I'm sure it is not as nice as living alone, but for the above benefits, I think if you screen carefully enough and they are cool people, it could be well worth it. At least worth a try. Plus in retirement, it would give me some people to occasionally go out with perhaps, or have a BBQ with, since I typically meet all my friends through work.
And if I needed/wanted to travel, there are still people there to look after things.