There seem to be a few people with very narrow views of cycling on this forum, but I don't think that's very representative. Most of the cyclists I know are multi-disciplinary, and it wouldn't even occur to them to worry about whether they are "roadies" or "MTBers" – they just enjoy messing about on bikes.
Anyway, why restrict yourself to only two categories when there so much to do? Cross, track, long distance cycle camping tours, triathlon, commuting, duathlon, time trials, XC, pootling along cycle paths with the kids, road racing, MTB marathons, Audax, sportives, big days in the mountains, Sunday social cafe rides with the bunch, youth hostelling, speedway, BMX, etc, etc…
All good fun, and I still haven't got round to trying the last two in that list.