As I see it.
The only purpose the Gemini/ DeMeo Crew served (other than above average earning: car theft, drugs, etc.) was as a Constitution-like check on the threat of John Gotti's crew. They were the "dark side" that Big Paul didn't possess himself. When the beast grew to big for Paul to handle, he couldn't even find anyone willing to whack out Roy and Co. Well… I mean... eventually someone did.