I just purchased a S. swertifolium. The roots look like the image in the link below. They are basically non existant from what I can tell, but I am still new to orchids and newer to mini's.
Will it be okay if wrapped in sphagnum and placed in terrarium (80-95% humidity) and placed in correct light?
The near lack of roots wouldn't surprise me as a bare root recent import. If it wasn't a recent import I'd be unhappy. Either way I'd contact the seller and see what they do. Yes, with sphagnum, high humidity and correct light the plant will probably recover quite nicely if there is no ongoing rot problem.