The much-anticipated clash collapsed in negotiations over Mayweather's demands for random Olympic-style blood testing.
Roach was at Madison Square Garden to promote Pacquiao's March 13 WBO welterweight title defense against former champion Joshua Clottey of Ghana, but the bespectacled trainer was happy to talk about tactics for a possible Mayweather fight.
"We watched some tapes," Roach told reporters. "His style gives us difficulties. He doesn't like to engage that much."
Pacquiao, 50-3-2 and the only man to hold world titles in seven different weight classes, is a brawler in the ring, while Mayweather (40-0) is a supremely skilled boxer.
"It would be a very scientific fight. The smartest guy wins that fight, not the strongest guy," Roach said.
"I don't like him that much, but he's a great fighter and is good at what he does. It was a big challenge. And we wanted that big challenge. Hopefully, it will happen some day."
Roach said getting at the slick Mayweather was the trick.
"You have to really set traps for him. When you catch him in the corner or on the ropes, you've got to really take advantage of it. Break the body down.
"Really press him and see if he really is that gym rat that trains so hard. Can he fight a fast-paced fight for 12 rounds? He fights at his own pace. You can't let him be comfortable.
"You've got to force him. But you can't go straight in, because he's a great counter-puncher.
"The game plan has to be perfect."