Jones is a difficult fighter to rate in my opinion.

As people have said, his resume could have been better, but also in saying that, he utterly dominated a lot of quality fighters in his prime years.
In terms of accomplishments and record, he could be top 20 of all time.
In terms of ability, he rates a lot higher... top 5 for me.

He was not a strategic boxer at all really and when it came to technique, he was all over the shop at times. However, the one thing that sets him apart from pretty much every other fighter that has ever stepped foot in the ring was his almost superhuman physical gifts. There has never been a boxer that combined every vital physical attribute as well as prime Roy did.
His hands were a blur with speed, his feet glided across the canvas with ballet like beauty, his reflexes would make cats jealous and to top it all off, he had dynamite in his fists.

I don't think he ever really tried to outsmart or plan strategically for opponents, he simply entered the ring with the mindset that they were going to try to hit him and he had to hit them back. No matter who he fought, his style was almost always the same. His sheer athletic ability granted him this simple and effective approach, and he was never really going to legitimately lose until either;
A) Someone was even more physically gifted (which was near impossible, right?).
or
B) His athletic ability dwindled because of age or weight drain (Correct!).

So yes,
If Roy were to fight any of the past greats at his prime, there is no doubt he could potentially have beaten them all, especially considering how much boxing has advanced over the years.
But alas, when it comes down to comparing records and achievements from different eras, he falls short of the likes of Ray Robinson, Muhammad Ali, Joe Louis and Henry Armstrong to name a few.