Olding, who touched down against both Glasgow Warriors and Benetton Treviso, starts at full-back in a back-three combination that is completed by winger David Panter and Rory Scholes.
Joyce, a starter for the province against Glasgow, has been named at blindside flanker. Darragh Leader and Peadar Timmins will resume on the replacements bench.
Speaking ahead of the clash with France, Ruddock said: "We have a tough battle on our hands against a strong French team.
"They have recalled to their squad a number of players with Heineken Cup experience. We need to reproduce our valiant effort we showed against England."
Friday's Under-20 match will broadcast live from Athlone on RTÉ Two, with coverage starting at 7.30pm.
IRELAND UNDER-20 Team & Replacements (v France Under-20s, 2013 RBS Under-20 6 Nations Championship, Dubarry Park, Friday, March 8, kick-off 7.45pm):
15 - Stuart Olding (Belfast Harlequins/Ulster)
14 - David Panter (Corinthians/Connacht)
13 - Tom Daly (Lansdowne/Leinster)
12 - Rory Scannell (Dolphin/Munster)
11 - Rory Scholes (Belfast Harlequins/Ulster)
10 - Steve Crosbie (Old Belvedere/Leinster)
9 - Luke McGrath (UCD/Leinster) (capt)
1 - Peter Dooley (Lansdowne/Leinster)
2 - George McGuigan (Newcastle Falcon/Exiles)
4 - Gavin Thornbury (UCD/Leinster)
5 - John Donnan (Ballynahinch/Ulster)
6 - Conor Joyce (Malone/Ulster)
7 - Josh van der Flier (UCD/Leinster)
8 - Ryan Murphy (Dolphin/Munster)
16 - John Andrew (Ballymena/Ulster)
17 - Ryan Furniss (Worcester Warriors/Exiles)
18 - Adam Boland (Lansdowne/Leinster)
19 - Sean McCarthy (Shannon/Munster)
20 - Peadar Timmins (UCD/Leinster)
21 - John Creighton (Malone/Ulster)
22 - Mark Roche (Lansdowne/Connacht)
23 - Darragh Leader (Galwegians/Connacht)
IRELAND'S RBS UNDER-20 6 NATIONS FIXTURES:
Friday, February 1, 7.10pm - Wales U-20s 17 Ireland U-20s 15, Parc Eirias
Friday, February 8, 7.35pm - Ireland U-20s 16 England U-20s 15, Dubarry Park
Friday, February 22, 7.30pm - Scotland U-20s 21 Ireland U-20s 20, Netherdale
Friday, March 8, 7.45pm - Ireland U-20s v France U-20s, Dubarry Park
Friday, March 15, 7pm local time/6pm Irish time - Italy U-20s v Ireland U-20s, Stadio dei Marsi