A root given as ᴱ√RESE “aid, support” (gloss marked with a “?”) in the Qenya Lexicon of the 1910s, but Tolkien later decided that it was confused with another root ᴱ√reðe which seemed to do with kinship (QL/79). After this change, forms derived from ᴱ√RESE “aid” probably still included ᴱQ. resta in the sense “support”, as well as ᴱQ. resta- “aid, come to aid of, rescue, save”. In the contemporaneous Gnomish Lexicon Tolkien has a similar set of words likewise derived from distinct reth- vs. redh- (GL/65), indicating the true form of ᴱ√RESE was probably ᴱ√REÞE, since þ became s in Qenya. As Gnomish derivatives of reth- Tolkien initially gave G. rest, G. resta-, G. reth- (GL/65), but these were deleted leaving only G. grest “succour, salvation”, G. gresta- “aid, help, succour, support”, and G. gretha- “save, rescue, preserve” (GL/42).
It is possible the root ᴱ√REÞE reemerged as √REK “recover, get out/away, save from ruin/peril/loss” given in Tolkien’s later writings as the basis for S. edraith “rescue, saving” (PE17/38).
Neo-Eldarin: For purposes of Neo-Eldarin I think it is worth positing a (Sindarin only) Neo-Root ᴺ√(G)RETH to salvage some of these Gnomish words.
The form reðe was a root added under ᴱ√RESE [REÞE] “aid, support” in the Qenya Lexicon of the 1910s, with derivatives of ᴱ√RESE having to do with “kinship” reassigned to reðe, such as ᴱQ. renda “related, of the same kin or clan” and ᴱQ. resse “kinswoman, cousin” (QL/79). In the contemporaneous Gnomish Lexicon Tolkien had a similar set of words likewise derived from distinct reth- vs. redh-, with the latter most likely being the basis for words like G. redhin “related” and G. ress “cousin (f.), relative” (GL/65). The root was given as RESE- “kinsman” in the Poetic and Mythological Words of Eldarissa (PME/79), but the addition of reðe may be later than that document.
Neo-Eldarin: For purposes of Neo-Eldarin, I think it is worth positing a Neo-Root ᴺ√RE(N)D to preserve these early kinship and cousin words, for which we have no later alternatives. It might be considered a variant of later root √RED “scatter, sow” (Ety/RED; PE19/91) and thus applied only to more distant kin.