He has been a member of the Screen Actor's Guild since 1974, American Federation of Television and Radio Artists since 1973, and onstage Actor's Equity Association since 1975.In addition, Dennis has produced, directed and/or shot two features, a dozen commercials, three Internet industrial promos, and over 400 actors on digital video for the Internet.

A partial list of his credits includes:

• Television: co-starring roles on TV in M*A*S*H, PBS' American Playhouse Series, Midnight Caller, Wolf, Seventeen Syllables, and How The West Was Won.
• Principal Motion Picture Credits: include Gung Ho, The Wash, and Eyewitness.
• In theatre: he's appeared in the Broadway show Sly Fox at the Shubert Theatre in Century City. Other theatre includes some of the most respected repertory and regional theatres in the country: The Actors Theatre of Louisville, The Pittsburgh Playhouse, The Buffalo Studio Arena Theatre and in New York at Lincoln Center, The Equity Library Theatre, LaMama Experimental Theatre Club and the Cubiculo.
• Produced over 40 plays

In the course of his career, Sakamoto has worked with Alan Alda, Richard Burton, Jose Ferrer, Morgan Freeman, William Hurt, Michael Keaton, Telly Savalas, George C. Scott, Sigourney Weaver, George Wendt, and James Woods. Sakamoto has also worked with leading directors including Ron Howard, Tony Scott, Peter Yates, John Boorman, and Arthur Penn.