Roy is wearing this "RTFM shirt" in the debut episode of The IT Crowd. The shirt features Chairman Mao and the text "RTFM" - Don't know what RTFM means? Google is your friend. RTFM Shirt via Zazzle
Episode 2: 10 Points Shirt
You can catch Roy wearing a Space Invaders t-shirt in the second episode of The IT Crowd. This shirt has an orange space invader with the text "10 Points" written below him (or her). Unavailable
Episode 3: The Imports Shirt
Sadly, The Imports shirt was made especially for this episode, and no such shirt exists for purchase. Seems to be one of the only shirts made only for the show. Unavailable
There are 256 stages in Pac-Man. Reach the final stage and this is what you will see. Roy is caught wearing this classic shirt in the 4th episode of The IT Crowd. Pac-Man 256th Level Shirt from ErrorWears