Plenty is known about the ATR's icing behaviour.
What is alleged so far... probable icing conditions..aircraft not de-iced... aircraft rolls one way and then the other...
IMHO probability that rolling was uncommanded and started at about t/o flap retraction... maybe a Ppruner with ATR experience could clarify t/o and flap-retraction procedures? Hoping this isn't another lax discipline/poor airmanship tragedy. TP