Which patio door should the lock be installed in?
The roller doesn't affect how you select and install the lock. Think of it as of a latch of weird form.

The conventional way would be to install the lock onto the door that opens first such that when you are in front of the door and the door that bears the lock has hinges on the right you have to rotate the key clockwise to unlock and counter-clockwise to lock and if the door has hinges on the left you rotate the key clockwise to lock and counter-clockwise to unlock.

This answer has great pictures for door opening directions.

The latter is all about "right-handed" v "left-handed" - with the lock selected correctly you will have it behave conventionally. You can of course install the lock with "wrong" rotation direction (right-handed where a left-handed should go or vice versa) - then it will work okay, but you will have to rotate the key opposite to convention which is a bit annoying. That's the only issue you might have - it has nothing to do with the roller.