I found a book today called Ultimate Sacrifice on google books. In the chapter on Cuba, I found some interesting facts on Roselli.

-He went really out of his way to cultivate a partnership with Carlos Marcello. Roselli was well liked by the Guatemalan army because he had exposed them to the thrill of illegal gambling. Consequently this gave him some power with Guatemalan officials. When Carlos Marcello turned up in 1956 looking for a chance to beat deportation, Roselli helped him gain a forged birth certificate from Guatemala. He also helped a Marcello-owned company gain a lot of influence within the country. In the end Marcello rewarded him with a partner share in The Tropicana Casino (Cuba).
-He held connections to just about everybody. Everybody knew Handsome Johny. In the 50's he was so powerful he was almost on the level of a don (speculation)
-Obviously his power fading as time went on and his connections were no longer useful to dons around the country

From the glamor of hollywood to the grime of chicago, mingling with latin america, running casinos all over the world and forging ties to not one but three or four dons. Honestly I can't name a mobster who was more diverse in their dealings. Flamboyant or not he was obviously very effective at whatever he set his mind to.

Sorry for the long post.