You can use Rook's abilities by shortcuts 1,2,3 and 4 for Ultimate. Same for companions CTRL+1,2,3 (I forgot the secondary combination). The wheel is easier and give you the option to analyze/change the target, select the abilities order, read the marks which indicate detonations or applicability of de-buffs.
Timing is everything. Also remember that some abilities can be interrupted or canceled by moving or incoming damage. Make sure Rook is not in the middle of dodge or fade step movement, your target is not moving (teleport, charge attack or standing up after knock down) and you're not in the middle of incoming AOE sequence. Also see the confirmation of abilities queue in tactical wheel. Make sure you place the abilities in right order to get the desired effect.
