The Irish recovered from the shock concession of an early try to roar back, with Sexton scoring two tries and kicking seven conversions to leave him needing 10 points to overtake Ronan O'Gara as Ireland's top scorer.
"Age is just a number, I'm just delighted to be back," the smiling Sexton said in a post-match TV interview.
Standing with his hands on his hips, Sexton appeared to show no signs of a hand injury sustained when touching down for his first try, and he came out for the second half to rack up more points in his quest to overtake O'Gara.
"We're delighted obviously to get a result and to get a points difference like that. We knew it was gonna be a tough game at the start, especially with Romania being very physical and they certainly didn't let us down in that regard," Sexton said.
Sexton was making his first appearance since suffering a groin injury in Ireland's Six Nations clash with England in March, and he was banned for three games after an angry confrontation with officials after the European Champions Cup final in May.
"Until you're in the heat of battle, you can train all you want but until you're in a proper match it doesn't test your properly," Sexton said.
"We know that there's a much tougher task coming on Saturday against Tonga, and then beyond that as well with the other two teams, Scotland and South Africa," he added.
