Keane played in Ireland's 1-0 friendly win over Romania, his first appearance in the green jersey since he walked out of the Irish squad two years ago.
"He was very happy to have played and I'm sure relieved to be back and to have got that match under his belt after two years," Kerr told reporters.
"I'm sure it wasn't an easy decision for him to make but he's made it, not just for himself but in the interests of the team."
Keane's fellow midfielder Matt Holland sealed the Irish victory with a sweet right-foot volley five minutes from time but it was Ireland's prodigal son who was the centre of attention.
No one had been quite sure what sort of reception he would get at Lansdowne Road, two years and 11 days after turning his back on his country following an infamous bust-up with former manager Mick McCarthy before the 2002 World Cup.
But 42,000 fans gave him a rapturous reception when he took the pitch for his 59th cap and cheered his early touches of the ball to chants of "Keano, Keano".
"I was happy with the reception they gave the whole team and Roy," Kerr said. "I don't see why he shouldn't get a good reception. It's two years. It's time for us to move on."
Keane nearly scored with Ireland's first real attack, drilling a low cross-come-shot across goal in the eighth minute which striker Clinton Morrison almost managed to bundle into the net.
He also came close early in the second half, hitting a close-range effort against Romanian defender Mirel Radoi after goalkeeper Bogdan Stelea parried a shot from striker Robbie Keane.
"He gave us a bit of presence and changed the play, made himself available and I think he showed why we wanted him back in the squad," Kerr said. "There was a good balance about us and he was part of that."
Kerr said he had not expected Keane, who picked up a knee injury in the English FA Cup final last weekend, to last the full 90 minutes.
"We'd agreed to play it by ear and see how he was feeling," Kerr said. "I think he was enjoying it enough and he didn't want to go off. He was fine at the end."
