The Blues centre, along with Scarlets playmaker Rhys Priestland were rated as only 50/50 for the game a week ago with knee injuries but both have won their race against time.
"It was touch and go," Roberts said. "I haven't played any competitive rugby since late December, but I went to Poland last week and had some good conditioning and recovery work.
"I started running at the end of the week and I have done some full contact work this week.
"I am just delighted to be part of such a huge match. I am sure I will be blowing a bit in the first 10 minutes, but then I will settle down. I hope I am good enough after six to eight weeks out."
Lydiate apart, Wales coach Warren Gatland has also lost prop Gethin Jenkins (knee), hookers Matthew Rees (calf strain) and Lloyd Burns (neck), plus locks Luke Charteris (wrist) and Alun-Wyn Jones (toe) from his Dublin plans.
Ten survivors remain from the team that claimed a comprehensive World Cup quarter-final win against Ireland in Wellington four months ago, with Jones, wing Alex Cuthbert, prop Rhys Gill and locks Bradley Davies and Ian Evans proving the exceptions.
Roberts added: "We not only need to emulate that World Cup game, but also improve on it, because nothing less will do.
"We need to produce the perfect game to beat Ireland, that is what it will take. We were very close to being perfect in the World Cup game, and we all need to put our hands up and produce again.
"Ireland away first up is one of the toughest challenges you can have in the tournament. Their players are playing well domestically, and they have the motivation of the World Cup and the defeat to us last year.
"The winning team in the first Six Nations game can get on a snowball, while the losers go away knowing that all the pressure is on them to win their next match to stay in the hunt."