The Etymologies seem to list this word as a noun, but it is clearly the third person singular of the verb
Noldorin
roch
noun. (swift) horse
roch
noun. horse, swift horse for riding
lobor
noun. horse, [heavy riding] horse
rohiroth
collective name. Horse-lords, Horse-masters
roheryn
proper name. Roheryn
blâb
verb. (he) flaps, beats
lhammas
noun. account of tongues
lhâf
verb. (he) licks
lhôd
verb. (he) floats
lobor
noun. horse
orthor
verb. (he) masters, conquers
osgar
verb. (he) cuts, amputates
síla
verb. (he) shines white
sôg
verb. (he) drinks
thia
verb. it appears
tôg
verb. (he) leads, brings
tôl
verb. (he) comes
According to WJ/301, the expression tôl acharn "vengeance comes" was later changed to tûl acharn by Tolkien
A word for “horse” in The Etymologies of the 1930s, derived from the root ᴹ√LOP (EtyAC/LOP). It did not appear in The Etymologies as published in The Lost Road, but Carl Hostetter and Patrick Wynne reported it in their Addenda and Corrigenda to the Etymologies (VT45/28).
Conceptual Development: The similar word G. lobros “steed, horse” appeared in the Gnomish Lexicon of the 1910s (GL/54), clearly based on the early root ᴱ√LOPO that was the basis for “horse” words in the Qenya Lexicon (QL/56). In The Etymologies, Tolkien first gave the root as ᴹ√LOB and the Noldorin form as {lum >>} lhuv, perhaps from ✱lōbo, but these were deleted and replaced by ᴹ√LOP and lobor.
Neo-Sindarin: Since Tolkien sometimes described S. roch as a “swift horse”, I’d assume lobor was a heavy riding horse or war horse.