Wales centre Roberts was joined on the scoresheet by England backs Mike Brown and Marlande Yarde, who both scored twice, while there were also tries for Luke Wallace, Tim Visser, Jack Clifford and Tim Swiel. Ruaridh Jackson and Swiel each landed five conversions.
Pool Two leaders Ospreys ran in 11 tries as they thrashed Grenoble 71-3 at the Liberty Stadium.
Scott Baldwin, Dan Evans and Hanno Dirkson scored braces along with tries for Olly Cracknell, Ashley Beck, Brendon Leonard, Scott Otten and Dan Biggar, who kicked eight conversions. Benetton Treviso gained their second victory in Pool One, prevailing 21-17 at home to winless Bayonne. The hosts scored all their points in the first half with David Odiete and Luca Bigi touching down before a penalty try was awarded. Tommaso Allan landed all three conversions.
In the Champions Cup, Stade Toulousain beat Zebre 54-15 in Pool 2, and Bordeaux-Begles succumbed to a 12-20 home defeat by Exeter Chiefs.