The "CO" flights via DTW are NW metal.

On CO, you'll be on the ERJ and B1900, so no upgrades.

DL flies MD-80s on ROC-ATL, but I believe it's all RJ's on the TOL leg and via CVG.

NW flies DC9s and ARJs on ROC-DTW, both of which are likely to give you a near 100% upgrade percentage as a NW or CO Gold (which is what you'd be comped as a UA 1P). The Saabs on DTW-TOL are loud, but more comfortable than a CRJ. And I'd rather connect through DTW than ATL any day.

Why are you not even considering NW? You could fly NW and credit your miles to CO or DL, but Skymiles elites don't get upgraded on NW, and OnePass elites get upgraded, but only earn 50% EQMs on cheap fares on NW metal.

NW and CO and DL have roughly reciprocal mileage earning, except that on cheap fares on CO metal you'll only get 50% Worldperks or Skymiles EQMs, while cheap fares on NW or DL metal will only get you 50% OnePass EQMs. Also, on CLE-TOL you're going to be on the B1900, which is a "CO Connection" flight and NOT eligible for Worldperks or Skymiles earnings. The B1900 is great if you enjoy feeling like you're "really" flying. Avoid it like the plague if you are afraid of small planes (a CRJ is a giant in comparison).