No, Borg could not volley as well as Roche, but his groundstrokes were far better, and his serve was quite good as well. His first serve was one of the best in the game, especially during about 1978-1981.
The game slowly evolved with wood racquets, overall till they were phased out in the early 1980's. The players overall were more athletic and fit, generally, with each successive era. So, no Lacoste probably could not compete well vs. Laver and Roche. Yet, I think Borg and Laver would be quite a tough match up, and I think Borg may very well have come out on top more often than not (Peak Borg vs. Peak Laver).
I would say the same applies for both McEnroe and Connors, but I don't think they would have fared as well against Laver as Borg. Then, you had the sea change in racquet technology, especially starting in about 1982 or so, and the increased athleticism continued as well.
So, IN GENERAL, the athletes of today are superior to the players of both the 1990's, 1980's and 1970's. Yet, they are not necessarily superior to those players as far as pure shot-making ability. Yet, I would not say the players of today are more athletic than Borg. No way, he could definitely "hang" with players of today in all athletic "departments", ESPECIALLY speed and stamina.
The thing that makes Borg stand out, in my opinion, is his nearly unparalleled athleticism (Nadal, Sampras, and Federer are in his league but not many others) , also combined with top-notch shotmaking ability with wood/wood + slight graphite inlay frame that was about 70 square inches (Donnay wood and then Donnay Borg Pro).
Now, put a modern frame in his hands (Head/Babolat/Wilson), growing up especially, and THEN add that to his quickness, speed, stamina, ability on all surfaces, upper and lower body strength, and mental toughness (clutch play) and you have in my opinion, the greatest player of all time, in terms of peak performance overall.
Now, as far as hard courts go, he did win about 9 hard court tournaments during his career, while losing 3 US Open finals on hard courts. Yet, he won a ton on Red Clay, Grass, and Indoor courts also, so he was a extreme threat on every surface, and every tournament. He won 11/27 GS tournaments played (best in the Open Era) and he won nearly 90% of his Grand Slam singles matches. Both are Open Era records.
Those are the reasons why, in my opinion, he is ever so slightly ahead of Laver, Sampras, and Federer. Yet, you can make plausible arguments for all four of those guys that are in my opinion, at "the top of the mountain": Laver, Borg, Sampras, and Federer.
I reiterate, you can make arguments for all 4. It's too bad we missed out on seeing him play from age 26-28 or so, when a player is still very fit and strong, but also has all that experience to draw from. But he made his choice to stop playing. He would have won more GS tournaments, in my opinion, but of course that's hypothetical. To say he WOULD NOT have won more I think is a less convincing argument to make, in my opinion.
When Borg retired, he had won 3 of 6 big slams, and McEnroe had won the other 3 (Borg won 2 FO's and a Wimbledon during 1980-1981, while McEnroe won 1 Wimbledon, and 2 US Opens). His WORST head to head record against ANY PLAYER was 7-7 vs. McEnroe, and guess what? That was ONLY on hard courts, grass courts, and indoor courts, with NO CLAY COURT matches.
Borg retired as the reigning FO champion, so he was easily still the best clay courter around. Plus, he would have still been a big threat at Wimbledon especially. In addition, he won the last 2 YEC tourneys he played in New York, beating both McEnroe and Lendl INDOORS. That was, in effect, the 4th major back then, since the top players did not play the AO during that time.
Basically until about 1980-1981, you have "apples to apples" pretty much, even though wood racquets SLOWLY evolved, some, they were still WOOD, and the tennis balls didn't change that much, and of course the courts were the same dimensions, although you saw a shift away from just grass/clay.
So, until 1981-1982, the 2 greatest players, in my opinion were Borg and Laver. Post 1981-1982, you had 2 other HUGE greats emerge in the Game, namely Sampras and Federer. That's how I arrive at my "top 4" male players in history.