Green’s Dictionary of Slang

1. extravagant, betting or spending heavily.

1970		E. Tidyman Shaft 46: The floating action for the high-rolling crapshooters.
1984		D. Jenkins Life Its Ownself 208: He was a high-rolling friend of ours [...] The year we went to the Super Bowl in Los Angeles, Elroy rented an estate in Beverly Hills and threw a party that lasted a week.
1994		N. McCall Makes Me Wanna Holler (1995) 102: A high-rolling, slick-dressing drug dealer.
2001		Source Aug. 118: Krayzie’s father, who in the video has benefited from his son’s high-rolling, illegal lifestyle, will be arrested.
2015		(con. 1919) C. Fountain Betrayal 91: If some of the numbers [i.e. bets] being called out [...] might make the average bleacher sitter blanch, it was nothing the high-rolling crowd at the Sinton hadn’t heard.

2. in ext. use, important, influential.

1890		‘Cad McBallastir’ Society as I Have Foundered It 33: In PauI was a tip-top, high-rolling Swell!
1969		B. Jackson Thief’s Primer 147: Then I know he’s a pretty high-rolling thief.
2004		B.S. McWilliams [bk title] Spam Kings: The Real Story Behind the High-rolling Hucksters Pushing Porn, Pills and @*#?% Enlargements.