Roberton came off second-best after a big collision with Tom Jonas during the second quarter, but was cleared to play on.
The defender then gave a bizarre half-time interview on the broadcast coverage of the match, in which he appeared dazed.
He was substituted out of the game during the half-time break, and Watters admits the club will review what occurred.
"I think it was about six minutes before half-time when he actually copped the knock," Watters said on Saturday night.
"Our head trainer actually spoke to him at the time and he gave all indications that he was OK. Then obviously coming off and doing the interview the knock had certainly rattled him.
"It's very hard sometimes, which is why it's such a fine line.
"Our players are our number one asset and we want to look after them, but it's a brutal game. We'll have to reassess that process, but our head trainer thought he was clear to go based on the assessment he did at that point."
The incident is likely to be scrutinised by the Match Review Panel, particularly given the resulting head injury to Roberton, but Jonas insists there was 'nothing in it'.
"I remember the ball getting kicked out and I heard a whistle and wasn't sure what it was for. Obviously he was coming at me and he didn't have the ball so I had to take his body in some other way," Jonas told AFL.com.au.
"Initially I just thought it was a fine bump but obviously these days with head clashes and high contact you're not too sure, so I'm sure it'll get looked at but I'm pretty sure there was nothing in it.
"I looked at him after the bump and he sort of tried to get up but couldn't, so I thought it might've stunned him a little bit."
Jonas believed Roberton escaped uninjured given St Kilda's decision to let him play on.
"I saw him get the ball a few times and he seemed to be moving okay, so I thought he must've been alright," Jonas said.
"But obviously with concussion these days, I figured he must've been no worries."