From my experience, its also about dynamics and personalities. If you have one roo that is fine to play second fiddle then there may well be no problem, as Whittni points out. I've had two cockerels (brothers) that were fine until one day when they had a real ding-dong (at 3.5 months old, i might add) that resulted in me having to cull both. My flock free ranges, so space was not an issue - just the pretender to the throne thought that he'd try his luck on that particular day. That situation may never happen again in my flock, but I thought it was worth sharing.
Since everyone's set up is different and the personalities of the cockerels / roos also different I'd suggest trying it and seeing how it goes and just be prepared to get rid of one of the roos, or segregate them if things start looking like a Rocky film.
All the best
CT