The three-times Wimbledon runner-up broke Lopez's wickedly sliding left-handed serve for the first time in the last game of the match to move into the third round of the tournament he has won four times.
"I'm so happy to be back in London at one of my favourite tournaments in the world," the former world number one said in a courtside interview in the west London sunshine.
Roddick was joined in the third round by Argentina's Juan Martin del Potro who beat Uzbekistan's Denis Istomin 6-4, 6-2 despite needing treatment after tumbling on the slick grass.