Green’s Dictionary of Slang

roast meat n.

the body in terms of sex.

1639		J. Taylor Crabtree Lectures 57: Thou art every day basting and basting, and yet caft afoord me no roaste-meat all the weeke long.
1707		N. Ward Wooden World 69: If ever he’s troubled with Dreams ... then truly he oft fancies himself a mauling off the Roast-meat in Smock-alley.

SE in slang uses

In compounds

roast-meat clothes (n.) [the meat in question being the ‘Sunday roast’ and the clothes one’s ‘Sunday best’ outfit; note naval jargon roast-beef dress, full uniform]

one’s best clothes.

c.1547		C. Bansley ‘Treatyse shewing and declaring the pryde and abuse of women now-adayes’ in Gentleman’s Mag May (1835) 47/2: In the next stanzas, however, he suddenly grows extremely pious, and denounces vengeance against all who ventured abroad in their ‘roast-meat-clothes’.
1673		J. Wade Vinegar and Mustard A2: Pray sir what day do you call this that your Roast-meat clothes must be put on? Is this not Munday.
c.1698		B.E. Dict. Canting Crew n.p.: Rost-meat-cloths, Holiday-cloths.
1710		Misfortunes of Simple Simon (1780) 4: Simon put on his roast-meat cloaths.
1725		New Canting Dict. [as cit. c.1698].
1737, 1759, 1760, 1776		Bailey Universal Etym. Eng. Dict. [as cit. c.1698].
1785, 1788, 1796		Grose Classical Dict. of the Vulgar Tongue.
1811		Lex. Balatronicum.
1812		‘Tim Bobbin’ Works 128: I will, that my executors cause me to be drest in my roast-meat clothes.
1823		Egan Grose’s Classical Dict. of the Vulgar Tongue.
1827		(ref. to 1680) Time’s Telescope 102: In the first place, appeared certain butchers, in their roast-meat clothes.
1848		(ref. to c.1700) T. Wright (ed.) Songs & Carols 83: The roast-meat clothes, mentioned in the first chapter, mean the holiday or Sunday clothes.
1850		St James’s Mag. 1 338: ‘What may be these same roast-meat clothes?’ ‘Why, holy-day clothes, to be sure’.
1876		Manchester Courier 20 Nov. 3/3: All had gathered round the bed bearing the coffined conjuror, attired in his ‘roast-meat clothes,’ jugs of jolly good ale were handed about.
2002		Best Aus. Stories 162: Morgana Morgan compelled Red Ned to shave daily, to plunge into a piping hot bath thrice a week, and wear roast meat clothes on the Sabbath.

In phrases

give roast meat and beat with the spit (v.)

to offer an apparent compliment and then to abuse its recipient.

c.1698

B.E. Dict. Canting Crew n.p.: To give one Rost-meat, and Beat him with the Spit, to do one a Curtesy, and Twit or Upbraid him with it.