Since the Wells, dozen of Aes Sedai had swore fealty to him. The Black Tower was supposed to be his weapon and they were getting more and more dangerous by day. The attack on the Sun Palace certainly proved that they were getting out of control. So why didn't he require their fealty?
The key point here is that when the Aes Sedai swear fealty they can't break that vow (unless they are Black Ajah.) The Oath rod required them to stay "loyal" to Rand because they cannot lie. The Ashaman were already assumed to be loyal to Rand, and specifically swearing fealty does not have the same effectiveness on them, since they are not bound by the 3 oaths like the Aes Sedai.
Essentially Aes Sedai as a whole are a force actively opposing and interfering with Rand, while the Ashaman as a whole are actively under his control.
oaths of fealty are not binding without an oath rod.
Near the end of the series, Rand himself acknowledges that he screwed up pretty big with the Black Tower, so you're not the only one asking this question.
There were two major factors behind Rand's decision not to go demand fealty from everyone there:
He considered the men in the Black Tower "his people" -- men he had rescued from madness and death, and given a purpose. Forcing people to swear fealty to him was something he did to those he didn't trust, like the various nations he conquered. He (at least initially) assumed that the men of the Black Tower would follow him willingly. In particular, he seemed to trust that people like Logain and Taim, even if they didn't personally like Rand, had the same end-goal in mind, and so he could trust them to achieve that goal.
Rand didn't want to be personally responsible for the success or failure of the Tower, since he didn't expect to survive much longer. There were a number of things Rand did over the course of the series (the school system, the Seanchan treaty, even getting Elayne on the Sun Throne) that were meant to set up the world to operate successfully after he was dead, and no longer there to threaten everyone into obedience. He treated the Black Tower much the same: he set it up and handed it over to others to run it for him.
His mistake, which he acknowledged much later, is that the men of the Tower were his people, but he essentially abandoned them. His refusal to spend any time there or take the lead in training them left them vulnerable to others, like Taim, to swoop in and take them from him.