This will be the first Major League start for Roach, the 24-year-old right-hander.
"He can probably give us 60 pitches that we can feel good about," Black said when asked what Roach's ceiling was for a pitch-count.
"He threw two innings the other night [May 15] and had two days off. He has started in his past and he's got a sinkerball where, if it's working, he should be efficient. We'll find out tomorrow."
Roach has worked exclusively out of the bullpen this season, posting a 2.57 ERA over 12 outings and 21 innings. He has allowed 24 hits, eight walks to go with 13 strikeouts. Roach's plus-pitch is his sinker, which could come in handy at Coors Field.
The Padres will likely have seven relievers available on Sunday in the event Roach needs helps. And the fact that Monday is an off-day for the Padres helps as well, Black said.
Roach is no stranger to starting, as he has made 54 Minor League starts in the Angels' system and later the Padres' system.
Corey Brock is a reporter for MLB.com. Keep track of @FollowThePadres on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.