Green’s Dictionary of Slang

1. (US Und.) to travel on the roof of a railway passenger carriage.

1913		L. Light Modern Hobo 36: I ‘roofed’ it to the next division point.
1916		‘A-No. 1’ Snare of the Road 43: I roofed the dining car of this fast Northern Pacific flyer.

2. (US Und.) to break into a building via the roof.

1969

B. Jackson Thief’s Primer 94: Say it’s a two- or three-story building and you’ve roofed it and you’ve come in.