A word for a “horseman, rider” in the Quendi and Eldar essay of 1959-60, a reduction of ancient ✶roko-kwēn “✱horse-person” (WJ/372, 407). In notes on the Disaster of Gladden Fields, Tolkien translated roquen as “knight” for a rank higher than a mere ohtar “warrior” (UT/282 note #17), though apparently all ranks rode horses. It may be that the sense “knight” applies only in a [Gondorian?] military context, while in ordinary use roquen can apply to anyone capable of riding a horse. A more general term for a “knight” as a noble person would be arquen.
Quenya
roquen
horseman [but the quenya word does not show gender], rider, knight
roquen
noun. horseman, rider; knight
quén
one, (some)body, person, individual, man or woman
quén (quen-, as in pl. queni; as final element in compounds -quen) noun "one, (some)body, person, individual, man or woman", pl. queni = "persons", "(some) people", "they" with the most general meaning (as in "they [= people in general] say that..."). The element is combined with noun and adjective stems in old compounds to denote habitual occupations or functions, or to describe those having some notable (permanent) quality; examples include roquen, ciryaquen, arquen, q.v. Also in aiquen "whoever", ilquen "everybody" (WJ:361 cf. 360, 372).
er
one, alone
er cardinal "one, alone" (ERE, VT48:6, VT49:54), in an early source also adv. "only, but, still" (LT1:269); Eru er "one God" (VT44:17; er was here emended by Tolkien from erëa, which seems to be an adjectival form *"one, single".)
erëa
cardinal. one
erëa adj.? "one" or *"single", apparently an adjectival form (see er) (VT44:17)
min
cardinal. one
min numeral "one", also minë (VT45:34, VT48:6)
minë
cardinal. one
minë numeral "one", also min (MINI, VT45:34)
mir
cardinal. one
mir (2) cardinal "one" (LT1:260; in LotR-style Quenya rather minë)
mo
one, someone, anyone
mo, indefinite pronoun "one, someone, anyone" (VT42:34, VT49:19, 20, 26)
a
cardinal. one
min
cardinal. one, one, [ᴱQ.] one (in a series), the first
roquen noun "horseman [but the Quenya word does not show gender], rider, knight" (WJ:372, UT:282)