"Mr Roberts is the Muggle site manager of a campsite near to where the Quidditch World Cup is being held."
From the Story
Discovered in Book 4, Chapter 7, Bagman and Crouch
"Mr Roberts directs Mr Weasley to their reserved place on the campsite. He is curious as he watches Harry help Arthur Weasley to understand Muggle money, and assumes that Arthur is a foreigner. He tells the group that Arthur is not the first person who has had trouble with money, and that he had two earlier campers try to pay him with great big gold coins, unaware that the majority of his visitors are wizards. He is curious about the number of people staying at the campsite, and thinks that there is some sort of rally going on. He notices that a lot of the visitors are dressed strangely, not like normal people, and that many of them know each other.
It is only after a Memory Charm is placed on him by a Ministry official that Mr Roberts hands over Mr Weasley's change, and a map of the campsite. The Ministry wizard tells Arthur that Roberts has been creating a lot of trouble for them, and needs a Memory Charm placed on him ten times a day to keep him from becoming suspicious."
Discovered in Book 4, Chapter 9, The Dark Mark
"Mr Roberts and his wife and children are attacked by the group of masked wizards amid the chaos at the campsite. They struggle as they are magically hovered in mid-air, and are contorted into grotesque shapes, as though they are puppets. The Robertses are targeted by the wizards because they are Muggles."
Discovered in Book 4, Chapter 10, Dress Robes
"The Weasleys, Harry and Hermione pass Mr Roberts at the door of his cottage as they leave the campsite. Mr Roberts has a strange, dazed look about him, and he waves them off with a vague 'Merry Christmas'. Mr Weasley tells them that Mr Roberts will be alright eventually, but as his memory had to be modified to forget the unpleasant events of the previous night, he might be disorientated for a while."