There are 2 great places that come to mind immediately: one is the Hotel Aenea, which if memory serves me correctly is on Via Cavour. The staff is super multi-lingual, very nice, and very professional. The hotel is clean and pretty new, so it's got a lot of amenities, and it's right near the Cavour metro stop....so maybe a 10 minute walk from Termini? Another is literally right around the corner from the Republicca metro stop and is called Suite Dreams-it's a really fantastic place! They're pretty highly regarded on Trip Advisor as well. Hope that helps!