Same thing last week in 300 , spoiler mixer replacement was required . Try cycling the spoilers up + down on the ground without moving the ailerons , go outside and look at the panels , if they have stowed correctly . The aircraft i had a problem with , the flight spoilers were not stowing correcly after deployment , this was first clue to problem .
The aircraft was displaying the exact same thing you describe , in flight with a/p engaged spoiler deployment resulted in approx 2 units aileron input by the a/p to keep wings level .
Engineers deduced flight spoilers not deploying symetrically and replaced spoiler mixer . I was told at the time by an engineer that adjusting the cables does not cure this problem as the correct rigging is to do with the mixer unit .
Hope this helps .
NF .
p.s. this is fairly basic 73 stuff , id be worried if your engineers dont understand it !