Howley had indicated he does not expect Roberts (mild concussion) and lock Jones (shoulder) to be available.
Jones is having a scan to assess the seriousness of his shoulder injury.
If Scarlets centre Jonathan Davies overcomes the groin problem that ruled him out of contention against Argentina, he could join team-mate Scott Williams in midfield against the Islanders.
But he has only taken a limited part in training, while Ashley Beck (hip) is on course to train fully this week along with Ryan Jones, who has returned from the Wales camp in Poland with a shoulder problem.
Howley hugely disappointed following Wales' loss to Argentina
Luke Charteris, who is available after playing for Perpignan at the weekend, and Cardiff Blue Bradley Davies will be in a battle to replace Jones.
Wales are having go through the autumn series without 2012 Grand Slam tight-head Adam Jones (knee) and player-of-the-Six Nations flanker Dan Lydiate (ankle).
After taking on Samoa, Wales face World Cup holders New Zealand on 24 November and Australia seven days later.
squad for autumn Tests:
L Halfpenny (Cardiff Blues), Liam Williams (Scarlets); A Cuthbert (Cardiff Blues), G North (Scarlets), H Robinson (Cardiff Blues); A Beck (Ospreys), J Davies (Scarlets), J Roberts (Cardiff Blues), S Williams (Scarlets); D Biggar (Ospreys), J Hook (Perpignan), R Priestland (Scarlets); T Knoyle (Scarlets), M Phillips (Bayonne), Lloyd Williams (Cardiff Blues).
S Andrews (Cardiff Blues), R Bevington (Ospreys), P James (Bath), A Jarvis (Ospreys), G Jenkins (Toulon), S Lee (Scarlets); R Hibbard (Ospreys), K Owens (Scarlets), M Rees (Scarlets); B Davies (Cardiff Blues), L Charteris (Perpignan), I Evans (Ospreys), AW Jones (Ospreys); T Faletau (Newport Gwent Dragons), R Jones (Ospreys), R McCusker (Scarlets), A Shingler (Scarlets), J Tipuric (Ospreys), J Turnbull (Scarlets), S Warburton (Cardiff Blues, capt).
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