Rome is not a city with a dense concentration of LGBT-specific retail. Gay Street has some, and there are scattered options elsewhere, but this is not Berlin or Amsterdam where shops of this kind cluster around the main gay areas. What exists is worth knowing about, and the general shopping environment in Rome is excellent even if it is not specifically gay-oriented.
What is on and around Gay Street
Via San Giovanni in Laterano and its immediate surroundings have a handful of shops selling pride merchandise, branded items, and some adult gear. These tend to be small operations and stock varies. Hours can be irregular, particularly in summer when things close for siesta and in August when some shut entirely.
If you are looking for something specific — party gear, leather, or adult items — it is worth asking in the bars or at a sauna reception. Staff know the current options and can point you to what is actually open.
General Rome shopping
For clothing and general fashion, Rome is one of the better cities in Europe. The area around Via del Corso and the Spanish Steps has international brands. Trastevere has smaller independent shops. Prices are standard for a major western European capital — not cheap, but not Tokyo-level either.
The shops
For the full Rome picture, see the Gay Rome Guide.