Help, baby's first tumble

I'm freaking out! My little guy just learned to roll. I sat him on the couch just to walk across the room and turn the light on and he rolled off. He's perfectly fine, he had a red mark on his forehead, but it's cleared up now. I picked him up and he calmed right down, smiled at me, giggled, we even played for an hour after. But then I had to go to work, my Mother-in-law says he's fine, my husband says he's fine, I'm just at work freaking out. I feel like such a bad parent because I could have prevented it, I just don't even know how to calm down.