Wales are third in Group D, four points behind Martin O'Neill's Republic of Ireland, who are top.
"Will a point be good enough? I don't think so," Roberts said.
"I will go as far to say that it's a must-win game for us if we are going to have any chance of finishing top of the group."
The former Leicester City and Watford player added: "But this group of players are used to big occasions and are used to big games.
"They've dealt with them admirably in the last two and a half years so they will be really looking forward to going to Dublin.
"I do believe we'll win the game on Friday. They will be under strength and we will be at full strength,"
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Forward Tom Lawrence is so far the only player to have pulled out of Wales' squad.
The Republic of Ireland have been hit by injuries with first-choice central defensive pairing Shane Duffy and Ciaran Clark ruled out.
Midfielders Harry Arter and Wes Hoolahan are both out injured too while Burnley's Robbie Brady is suspended.
But Roberts, who won 15 Wales caps between 1989 and 2001, believes O'Neill's side will be formidable opponents at the Aviva Stadium.
"A point is good enough for them I think," Roberts told BBC Radio Wales Sport.
"They've had a great start to the campaign and have won their last three.
"They went to Austria and won 1-0, which probably ended Austria's hopes of qualifying.
"The Republic are a very hard side to beat at home and haven't lost at home since September 2013, a run of nine games.
"They've got a solid side and Martin O'Neill gets his team working extremely hard, gets them very organised offensively and is a magnificent motivator.
"But I do think we've got better quality."
Former Wales striker Iwan Roberts says Friday's World Cup qualifier against the Republic of Ireland in Dublin is a "must-win" game.