A new documentary on Dennis Hopper, Nick Eberling’s “Along for the Ride,” starts Friday, Dec. 15, and the Roxie Theater is celebrating with a mini-retrospective of the iconic actor and director’s work. The retrospective begins with a double feature of “Along for the Ride” and David Lynch’s 1986 weirdness “Blue Velvet.” There will be a Q&A in between the films by Eberling, Hopper right-hand man and co-subject of “Ride” Satya De La Manitou, and producer Sheri Timmons.