According to Winnipeg Free Press, which is a daily newspaper in Winnipeg, Manitoba, the same city Adam Beach grew up in and lives, have stated a source have informed them that Beach will be playing Slipknot (not the heavy metal band) in Suicide Squad.
In the DC Comics universe Slipknot is a supervillain, who’s real name is Christopher Weiss, who worked for a chemical company in the Southern United States, where he develops his formula for durable ropes which he ends up using as a villain, hence the name Slipknot.
As for Slipknot involvement with Suicide Squad in the comics (via wikipedia):
“The Final Price” Suicide Squad 9 (January, 1988)
Slipknot comes under the attention of the Suicide Squad. Slipknot is taken along when the threat of the Manhunters arises on earth during the Millennium crisis. A stronghold of Manhunter robots is discovered deep in American swamplands not far from the Suicide Squad’s own base located in the Belle Reve prison. Slipknot and the Squad, including members such as Bronze Tiger, Rick Flagg, and Captain Boomerang are sent in to escort the “Baby Huey” (a car-bomb laced with an experimental high yield explosive) on a search and destroy mission. Slipknot discusses the ‘arm band bombs’ with Captain Boomerang. These deterrent devices are placed on the less trustworthy members and are set to explode if the person goes too far out of range. Captain Boomerang statesthat he believes the bombs are fake. This is enough for Slipknot. When he discovers his talent for strangling is useless against robots he makes a run for it into the swamp. The device begins beeping and flashing an alarm but Slipknot ignores the warning and once he gets out of range, his right arm is blown off. Boomerang, who had not been sure of the bomb’s reality himself, thinks ‘better you than me’. Following the success of the mission, in which the Manhunter base is destroyed and the Squad’s medic Karin Grace is sacrificed, Slipknot is found, weakened and bleeding but still alive.
Adam Beach’s role in Suicide Squad hasn’t been confirmed by Warner Bros. or anyone attached to the film. Though we believe at the least his local paper should have closer sources (or a source) to Beach than some other media outlets… but still– grain of salt until officially confirmed.