Thanks Michael for looking up Douglas Richardson volumes and reviewing all those sources.
I did have another look at soc genealogy medieval, and it looks like the sole source for Rohese being the daughter of William de Boulogne and sister of Pharamus de Boulogne, is a charter where Godfrey de Lucy, Bishop of Winchester (known to be a son of Richard de Lucy and Rohese) refers to Pharamus as his 'avunculo nostro' usually translated as uncle. See the end of this post from the late Leo van der Pas dated 29 July 2005
There is also quite a long discussion, titled 'Faramus of Boulogne and Richard de Lacy' which partly covers the fact that avunculus didn't just mean uncle or necessarily maternal uncle. It also points out that the name of Faramus de Boulogne's mother is unknown, as is the name of Richard de Lucy's father, which means there could be some other relationship. The very last post by Peter Dale, dated 15 Apr 2017 sets out the points for and against clearly, though without coming to any conclusion.
I would favour the we continue to use Unknown as the LNAB for Rohese, and explain the possibility of connection of the Boulogne family in Research Notes. The other possibility is that we do connect them up, and mark the relationship as Uncertain.