Written and first recorded by Tim Moore (1975).
Hit version by Bay City Rollers (US #28/CAN #6/AUS #9/GER #13 1976).
From the wiki: “‘Rock and Roll Love Letter’ is the second single from American Tim Moore’s second album, Behind the Eyes, written by Moore. Moore’s original version when released as a promotional single in 1975 did not chart. But, ‘Rock and Roll Love Letter’ was later covered in 1976 by the band Bay City Rollers, and that version became a Top 40 hit.”
Bay City Rollers, “Rock and Roll Love Letter” (1976):