The loose forward, 29, plays his testimonial game against Rovers at Hull College Craven Park tomorrow as both sides commence their pre-season programme.
Milner has made more than 250 appearances for Tigers since debuting in 2010 and also earned three caps for England.
Winger Crooks played alongside him at Wheldon Road in 2016 and said: “He’s a good lad is Adz.
“He is one of those who is always acting about and a great character to be around. He lifts the boys up when the place is feeling down and is daft as a brush.
“He can come across as a bit clever sometimes but he really is a few bob short of a full note.
“Everything he does, though, is always for the boys and people have seen what he can do on the field. He’s a very serious player, a good player and you have to be to play for your country and go as long as he has, especially at one club like Adz has.
“It’s a very under-rated thing to be able to do that, especially in the modern day game, to be able to go all your full career at one club and have as big an impact as Adz has at Cas. It’s great.
“It’s random not having fans there for a testimonial game but thankfully he’s found a way around that with it being streamed and hopefully people can pay that way to support him.”
Crooks, 27, is looking forward to getting started with a new-look Robins side that has seen England winger Ryan Hall and NRL trio Brad Takairangi, Albert Vete and Korbin Sims all join up.
The former Hull FC player said: “It is going really well.
“We’ve been impressed with how we’ve gone in training and everyone is just itching to get a run out to give us a good proper test to see where we are before the season starts.”
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