Perhaps best known as ticket scalper Mike Damone in the 1982 comedy Fast Times at Ridgemont High, Romanus starred in the 1983 series The Best of Times as Pete Falcone. His other TV roles include Fame (as Miltie Horowitz in 1986–1987) and two short-lived shows: the 21 Jump Street spin-off Booker (as Tony DeAngelo in 1989) and as Jeff Foster in Maggie Winters in 1998.
In 1983, he also appeared in Styx's rock opera music video for Kilroy Was Here.
Romanus has starred on soap operas such as Days of Our Lives as Marvin 'Speed' Selejko from 1983–1985, and The Young and the Restless as Lou in 2002. He has guest starred on many shows, including CHiPs,The Facts of Life, 21 Jump Street, Alien Nation, MacGyver, Providence, Will & Grace, and My Own Worst Enemy. Romanus directed the 2008 drama Grapefruit Moon and had a small part in American Pie Presents: The Book of Love, as himself. In 2010, he played the guitar teacher in The Runaways.