Fly-half Priestland and centre Roberts have recovered from knee injuries to take their places in coach Warren Gatland's starting line-up at the Aviva Stadium in Dublin (kick-off 3pm).
But the team announced by Gatland does not include flanker Dan Lydiate, who is sidelined by an ankle problem, while Saracens prop Rhys Gill makes his first Six Nations start.
Lydiate joins Gethin Jenkins (knee), Luke Charteris (wrist), Alun-Wyn Jones (toe), Matthew Rees (calf strain) and Lloyd Burns (neck) in missing the Dublin trip.
Roberts, meanwhile, has not played since Christmas, while Priestland was hurt during the Scarlets' Heineken Cup victory over Castres a fortnight ago.
But their recoveries provide a huge lift for Gatland as Wales look to repeat their World Cup quarter-final victory of just four months ago over Ireland.
There are five changes from that game in Wellington, with Alex Cuthbert replacing retired wing Shane Williams, Gill taking over from Jenkins, Bradley Davies and Ian Evans teaming up at lock and Ryan Jones in for Lydiate.
Hooker Huw Bennett will win his 50th cap - only the second Wales hooker to achieve that feat after Garin Jenkins - with Cuthbert starting on the right wing and George North switching wings to wear the number 11 shirt.
Gatland said: "We have been able to retain continuity in some key areas.
"We have been working hard, and we feel we are approaching this match with the right attitude and with some good preparation work done.
"We are two sides who know each other well.
"Ireland will not have enjoyed losing to us in New Zealand. They will want to redress the balance in Dublin this weekend, but they will find us in just as determined a mood."
Wales have won on just two of their previous six Dublin visits in the Six Nations, while Ireland can claim seven previous victories on the tournament's opening weekend.
Wales team: L Halfpenny (Cardiff Blues); A Cuthbert (Cardiff Blues), J Davies (Scarlets), J Roberts (Cardiff Blues), G North (Scarlets); R Priestland (Scarlets), M Phillips (Bayonne); R Gill (Saracens), H Bennett (Ospreys), A Jones (Ospreys), B Davies (Cardiff Blues), I Evans (Ospreys), R Jones (Ospreys), S Warburton (Cardiff Blues, capt), T Faletau (Newport Gwent Dragons).
Replacements: K Owens (Scarlets), P James (Ospreys), A Powell (Sale Sharks), J Tipuric (Ospreys), L Williams (Cardiff Blues), J Hook (Perpignan), S Williams (Scarlets).
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