I use KingEric's awesome "FreeFlyCam" plug-in.  It allows you to tilt the camera in free camera mode (tfc command).  He has versions available for Fallout and Skyrim.  (Requires Fallout 4 Script Extender)   Download Link: http://enbseries.enbdev.com/forum/viewtopic.php?f=6&t=5386