While he was receiving treatment, Dragons full-back Martyn Thomas collided with Roberts and the medical staff and he eventually limped off.
Luke Charteris and Alun Wyn-Jones are already doubtful for Wales' Six Nations campaign and head coach Warren Gatland will be keeping his fingers crossed his ranks are not further depleted by the loss of Roberts, who has 39 caps.
And Blues co-coach Gareth Baber revealed there would be no quick decisions on Roberts.
"Jamie took a bang on the knee which he has had a problem with before," he said. "We've got to let it settle down and see how it is next week."
Meanwhile, there was better news for Gatland after Gavin Henson came through his Blues debut unscathed and could yet force his way into Six Nations reckoning.
"Gavin looked what we know he is," added Baber. "He's got a great skill set and he showed them all.
"It was a tough, physical game and there wasn't as much width in it as we would have wanted. But what he had to do, he did well. He looked assured, he looked confident and, if you have a confident Gavin Henson, teams will worry about him. He just needs to keep healthy and get playing."
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