There are several advantages for chooing NWA for ROC-TOL:

1.) Despite Detroit's reputation for bad weather, DTW is one of the best large airports in the country for on-time operations. NWA is regularly one of the top legacy carriers for on-time performance.
2.) The five year old Northwest World Gateway Terminal (also known as McNamara terminal) is airy, spacious, easy to navigate, has good restuarants near the NWA gates, and has four comfortable WorldClubs.
3.) As other posters have noted, your upgrade opportunities on DTW-ROC are very good.
4.) VERY IMPORTANT: TOL is only about a 50 mile drive from DTW. If there are flight irregularities, missed connection, or you need to change your business schedule, you can easily drive to/from DTW and not loose half of a day.