I'll pose a related question: roll-catch or do both simultaneously? I tend to go for roll-catch, but that may be due to poor shoulder flexibility.
The kick can be used to accelerate your recovering arm out of the water (roll-kick) or to push you over your anchor (kick-roll?) I think that is the choice.
One last question: Not sure about this, but I may sometimes have two pulses in one kick. In the first, my whole leg goes down and my knee starts to bend, in the second my knee straightens out much like a whip. So one can start the roll and the second can come after it? Or is this a crossover?