Janssen, 23, had one goal and a team-high 114 penalty minutes in 48 games with the Devils last season.
Marshall, 34, had 24 points (8-16) and 31 penalty minutes in 59 games with Lowell of the AHL last season. The 10-year NHLer had 239 career points (92-147) in 700 games with Dallas, Columbus and New Jersey.
Magnan, 21, had 12 points (2-10) in 69 games overall with both ECHL Trenton and AHL Lowell.
Grand-Pierre, 30, spent the past three seasons in Europe, last season recording 23 points (9-14) and 63 penalty minutes in 44 games with Dusseldorf in the German League.
Moran, 34, had five points (1-4) and 10 penalty minutes in 18 games with AHL Portland last year. He also played in Germany.
Clarke, 27, had two goals in 13 games with the Los Angeles Kings last season while also putting up 57 points (24-33) in 63 games with AHL Manchester.