Crosswise's body, legs & head and Rook's head use the pale grey of Sideways' hands and windshield chest panels.
Crosswise's & Rook's knees, arms and hips are the dark grey of Sideways' upper legs & handlebars.
Rook's legs & body and Crosswise's upper legs are the black used for Sideways wheels and upper arms. They're articulation and function is identical. Crosswise is the grey one that should have purple striped on it's legs. Rook is the black one that should have red. Early versions of Crosswise had red stripes which is confusing as the colour indicates which faction they align with - Crosswise to Decepticon and Rook to Autobot.
Both have ball jointed and bending knees, ball jointed hips and arms that turn at the shoulders. This enables either one to ride the bike pinion with the other - a small tab on their bottom fits into slots on Sideways.
Both have a Minicon port on their rear. Apparently there's some sort of weapon mode for them which I guess involves opposing the legs scissor style.
They can combine to form a third rider for Sideways: Fold Crosswise's arms back and Rook's forward. Spread rook's legs apart. Turn rook upside down and with him facing forward and Crosswise facing the rear put the toys together head to head which will cause the combined head to rise out of Rook's bottom. Fold Crosswise's face up so it locks into Rook's back to stabilise the toy. The combined form has Crosswise's leg articulation, ball jointed shoulders and a bending then ball jointed elbow.
When Sideways is in robot mode each Minicon can combine with him: Point their arms straight up, spread the legs out to the sides and fold the lower legs down. Turn the Minicon upside down, place their head into the top of Sideway's head and push down lowering Sideway's original head and their arms into Sideway's body and raising a panel within the wind shield on Sideways chest revealing the allegiance associated with the head. In theory. Several early versions of the toy had the wrong Minicon activating the wrong symbol. Confusing ! Even now I look at these and reckon Crosswise looks a better Autobot and Rook a better Decepticon.
Overall: Two *very* odd Minicons, but ones that serve a specific purpose.
Rapid Run and his Minicons had a very limited release in the US being quickly replaced by Energon Starscream (Treadbolt and Ultra Magnus were likewise limited release repaints of Armada toys). In the UK however Rapid Run & co were available for all of Energon wave 1 alongside Inferno and Hotshot with Starscream being a wave two toy. See various Energon reviews for discussions about UK Energon cases !