"There were a couple of times they were down there waiting for the penalty," Robinson said.
"It is disappointing, but we can't change that, all we can do is do what we do.
"There is no way he (Ennis) was concussed."
Minichiello added: "Obviously Mick Ennis, there was a bit of gamesmanship there, playing for penalties."
When concussion rules were introduced at the start of the season, many pointed to the potential for them to be exploited, Robinson said the NRL needed to ensure that was not the case.
"There is always that risk but we had to bring it in, that was the important thing," he said.
"I wasn't sure if I was for it or not but we have learnt a lot about safety this year and we needed it.
"We need to get those guys off that do get concussed.
"We just have to have some integrity in our clubs to make sure we use it properly."
The Bulldogs have already been fined for not adhering to the rules this year.
But Dogs coach Des Hasler denied his players had taken a dive.
"Those sorts of players don't take dives. It's not in their make up, it's not in their game," he said.
The incidents somewhat overshadowed a commanding performance from Sonny Bill Williams against his old club before 19,088 fans.
Williams scored two tries and a brilliant offload to Shaun Kenny-Dowall led to another.
"It has been a tough week for us and he played a great game," Robinson said.
"He enjoys playing the Bulldogs."
In a brutal battle up front, with Roosters prop Jared Waerea-Hargreaves and David Klemmer going toe-to-to, the Roosters lead 10-8 at the break and scored 18 points in eight minutes midway through the second half to claim their sixth win of the season in the round 11 clash.
A 67th minute Tim Lafai sin-binning for a professional foul cost the Dogs and the struggled for fluency in attack minus their NSW halves Trent Hodkinson and Josh Reynolds.
Dumped Blues duo Mitchell Pearce and James Maloney responded to their State of Origin axings with solid games.
Klemmer was placed on report for lifting his leg while running in possession late in the game.
-AAP