Puerto Rican Cotto was docked a point for low blows in his successful defence against Zab Judah in 2007, but maintained the blows had been accidental.
"Cotto stops his opponents' momentum with that kind of blow," American Roach told Monday's Philippine Daily Inquirer.
"In that Judah fight he had five low blows."
Roach said he would raise the issue at a rules meeting before the November 14 showdown in Las Vegas.
The highly anticipated bout pits Pacquiao, widely regarded the world's best pound-for-pound fighter, against Cotto, who retained his WBO title in June with a split decision over Ghana's Joshua Clottey.
(Reporting by Ian Ransom; Editing by Ossian Shine)