The former Sheffield Sharks forward led the league in efficiency, rebounds and assists, averaging 18.5PPG, 14.7RPG and 6.7APG.
Marsden and teammate Mathew Martin (20.6PPG) also made the Team of the Year.
Eagles finished the regular Division Two North season in third place before losing to Manchester Magic 78-72 in the play-off semi-finals.
The club is planning on entering another team in Division Three of the National Basketball League next season.
"I’m very proud of all these guys have done,” said head coach Bob Martin.
Doncaster Eagles, pictured above. Back (l-r): Oliver Hylands (captain), Tom Hodson, Rob Marsden, Andrew Whalley, Noah Saa, Jack Stanley, Mathew Martin. Front (l-r): Eddie Brownell, Josh Metcalf, Zak Whalley, George Colwill, Sam Speight.