"The next three licks involve the technique of barring the 5th fret and rolling the first finger across he 5th fret onto the required strings instead of playing on the tip of the finger. This technique is very common in lead guitar playing. Practice it slowly at first."

The above is an extract out of the book I'm learning from (Guitar Method: Lead) but I didn't understand what it meant by rollig. I've spoken to my uncle who's ben playing for 30+ years now and he said he's never heard of it, so could anyone shed some light on this technique, please?
My setup:

Fender Telecaster Blacktop
Epiphone Les Paul Negative
VOX Valvetronix VT-30
Fulltone OCD
Boss FZ-5