One of Armato's first major hits was "I Still Believe", which reached number 13 on the Billboard Hot 100 for Brenda K. Starr after being featured on her self-titled album.[1] The track was later covered by Mariah Carey. Armato wrote the song about her first love, later recalling that she "felt every word of it".[1]
In 1999, Armato described spending more and more time in the studio helping young artists develop their talents, describing the studio as a "second home". An executive from EMI described her career trajectory as going "from lyricist to songwriter to producer."[1]
Armato co-wrote "Bet On It" from High School Musical 2,[9] and several songs from Miley Cyrus' debut double album Hannah Montana 2: Meet Miley Cyrus, including "Bigger than Us", "See You Again", "East Northumberland High", "Let's Dance", "Right Here", "Clear", and "Good and Broken".[10]
Armato has worked with Adam Lambert and the Beach Girl5 (known as BG5). Rock Mafia wrote and produced Miley Cyrus first single, "Can't Be Tamed"[11] which went top 10 on Billboard and No. 1 on iTunes.[12] She wrote and produced six additional tracks on Cyrus's album Breakout.[13] She produced Bonnie McKee's debut album Trouble along with Rob Cavallo.[14]
Armato co-wrote and produced the platinum song "Naturally" from Kiss & Tell, Selena Gomez & the Scene's debut album.[15] Between 2011 and 2012 Rock Mafia wrote and produced different songs for the soundtrack of the television series Shake It Up, among which are "Not Too Young", "Twist My Hips" and "The Star I R". In 2015, Armato co-wrote and produced several songs on Gomez's second solo album Revival. That same year Armato co-wrote and produced "Beautiful Now" and "True Colors" by Zedd.