Mr. Roberts is the Muggle campground employee who helps many of the wizards attending the Quidditch World Cup to their campsites. He's smart, and he keeps noticing that something's odd about all of these people suddenly flocking to his campground in the off-season. Ministry of Magic officials have to modify his memory repeatedly to keep him from suspecting anything, since Muggles aren't supposed to know about wizards.
His family also becomes a target for the Death Eaters, who decide to torture Muggles for a bit of fun after the Quidditch World Cup. They levitate the whole Roberts family – father, mother, and two children – sixty feet into the air and then laugh at their fear. The Ministry wizards are able to rescue the Roberts family, but they have to cast severe memory charms on all of them, which appear to leave Mr. Roberts really dazed once again.