Hey, here's a two in one lesson.
Vibrato is the quivering expressive sound of a note fluctuating in pitch.
Some people just have no patience, I'll tell you if you'll just wait a second. Fret the note and pick it. The rolling can come from your wrist, hand or a combination of the two, the finger should roll rather than move along the length of the string. Try this tab bellow off the Skeezix Dilemma Part 2 by Tourniquet on for size. Don't forget the vibrato at the end.