Ulster will also be looking for a home win when the Scarlets visit Ravenhill, while the visitors will be hoping to boost their campaign with a first ever league win in Belfast.
Friday's other games see European champions Munster travel to Edinburgh, while the Newport Gwent Dragons entertain Glasgow Warriors.
The round is concluded on Saturday evening when reigning champions Leinster visit the Arms Park where Cardiff Blues will be waiting to overturn the champions in the opening round for the second successive season after beating the Ospreys at this stage last year.
MAGNERS LEAGUE ROUND 1 FIXTURES:
CONNACHT v Ospreys, The Sportsground, kick-off 6.30pm
Edinburgh v MUNSTER, Murrayfield, kick-off 7.30pm (live Setanta Sports 2)
Newport Gwent Dragons v Glasgow Warriors, Rodney Parade, kick-off 7.05pm (live BBC Wales)
ULSTER v Llanelli Scarlets, Ravenhill, kick-off 7.30pm (live Setanta Sports Ireland)
Saturday, September 6:
Cardiff Blues v LEINSTER, Arms Park, kick-off 6.30pm (live Setanta Sports Ireland/S4C)