Middle English roste, "a chicken's perch," from late Old English hrost "wooden framework of a roof; pole or perch upon which domestic fowl perch or rest for the night," from Proto-Germanic *hro(d)-st- (source also of Old Saxon hrost "framework of a roof, attic," Middle Dutch, Flemish, Dutch roest "roost," Old Norse hrot, Gothic hrot "roof"), a word of unknown origin. Extended sense "hen-house" is from 1580s; that of "fowls which occupy the roost collectively" is by 1827.
To rule the roost is recorded from 1769, according to OED apparently an alteration of earlier rule the roast "be the master, have authority " (c. 1500), which, OED reports, was "In very common use from c 1530 onwards." However, Fowler (1926) has doubts: "most unliterary persons say roost & not roast ; I have just inquired of three such, & been informed that they never heard of rule the roast, & that the reference is to a cock keeping his hens in order. Against this tempting piece of popular etymology the OED offers us nothing more succulent than "None of the early examples throw any light on the precise origin of the expression'." The spelling in the earliest example is reule the roste.
1520s, "occupy a roost, perch as a bird," from roost (n.). Related: Roosted; roosting. Chickens come home to roost in reference to eventual consequences of bad actions attested from 1824; the original proverb seems to have been curses, like chickens, come home to roost.
"cock, male of the domestic hen," 1772, agent noun from roost (v.); earlier roost cock, c. 1600, in sense of "the roosting bird." Said to have become favored in the U.S. (it was noted by 1836 as a Yankeeism) and said to have been originally a puritan alternative to cock (n.) after that word had acquired the secondary sense "penis" (and compare roach).
"to roost, to alight or settle on or as on a perch; to occupy some elevated position," late 14c., from Old French perchier "to sit on a perch" (of a bird), from perche (n.); see perch (n.1). Related: Perched; perching.
late 13c., rosten, "to cook (meat, fish, etc.) by dry heat," from Old French rostir "to roast, burn" (Modern French rôtir), from Frankish *hraustjan (cognate with Old High German rosten, German rösten, Middle Dutch roosten "to roast"), originally "cook on a grate or gridiron," related to Germanic words meaning "gridiron, grate;" such as German Rost, Middle Dutch roost, from Proto-Germanic *raustijanan"to roast." Compare roster.
"Also freq. in mod. use to cook (meat) in an oven, for which the more original term is bake" [OED]. Intransitive sense of "be very hot, be exposed to great heat, become roasted" is from c. 1300. Of coffee beans by 1724. The meaning "make fun of (often in an affectionate way) for the amusement of the company" is from 1710. Related: Roasted; roasting.
Roast beef is recorded from 1630s; French rosbif is from English.
Bifteck and rosbif, words that have come into French after the invasions of 1814 and 1815, are only imitations of the English way of pronouncing "beef-steak" and "roast beef," the French not recognizing their word rôti, formerly rosti, in the English sounds of "roast" nor bœuf, in that of "beef," which in Norman-French was written bœf and buef, and probably pronounced somewhat like the present English. [Jean Roemer, "Origins of the English People and of the English Language," London, 1888]