4. Ryan Rolison
Minors (A, A+): 131 innings, 8-8 record, 4.40 ERA, 1.351 WHiP, 40 walks, 132 strikeouts
Ryan Rolison is the Colorado Rockies best pitching prospect by a wide margin.
Selected with the 22nd overall pick in the 2018 MLB Draft, Rolison was the third lefty starter taken by the Rockies in the first round during the decade. The other two, Kyle Freeland and Tyler Anderson, became a part of the Rockies rotation. The hope is that Rolison can follow in their footsteps.
It is easy to see why that would be the case. Rolison was an advanced collegiate pitcher, a lefty who used his four pitch arsenal to great effect. His fastball sits in the lower 90s, but Rolison has excellent command with the pitch, spotting it wherever he wants. His curve is easily his best pitch, as it features excellent depth and was considered one of the best curves in his draft class. Rolison also throws a slider and a fading change, two offerings with the chance to, at minimum, be average pitches.
As intriguing as Rolison is, he may actually be a better prospect in another system. His curve is his best pitch, which does not play well at Coors Field. In fact, according to a Fangraphs study done on various pitches in Colorado, the curve has 2.32 inches less break there than in other ballparks. For a pitcher like Rolison, that could be disastrous moving forward.
That does not take away from the type of prospect that Ryan Rolison can be, as he is easily the Colorado Rockies best pitching prospect. It does, however, mean that expectations should be tempered given his arsenal.