RockFarmer Properties filed plans for a 94,000-square-foot luxury condominium building in Astoria, making it one of the Queens landlord’s few condo projects. The firm, led by John Petras and George Michelis, is planning a mixed-use property at 21-21 31st Street with 43 apartments. DXA Studio would serve as the architect of record and Halstead Property Development Marketing would handle condo sales.