Henderson, who is Liverpool captain and a vital member of the Three Lions squad, is at Euro 2020 despite being nowhere close to full fitness.
Keane said earlier this month: "I was convinced Jordan was going to play the other day (against Austria, in a pre-tournament friendly). I think it's a huge distraction - he's clearly not fit.
"I don't think he should be involved. If he can't start against Romania, he's not fit.
"Physically and mentally, this game won't be that tough for him to deal with, he's an experienced player.
"He's not kicked a ball for three and a half months and he's going to European Championship? He can't be right.
"I've heard a lot of people say they want him around the place. For what?
"Does he do card tricks? Does he have a sing-song? Does he do quizzes in the evening? What does he do?
"Liverpool won't be happy either. Surely Jordan doesn't want to be around the place being some sort of cheerleader, you want to play and clearly he's nowhere near it."
Speaking on the matter, Maguire explained: "It is important to have leadership in the group and I think we have that in the squad, with a lot of captains at club level which brings that experience.
"Jordan is back to fitness and has been training for a while, and I'm back too.
"The other players have put us in a good position in the group and we are ready to keep going.
"It's a big squad we have here with 26 players and a lot of those are playing at a major international finals for the first time.
"But you only have a great time if you have a great tournament and we are here to win football matches."