Boll, a seven-time European singles champion and three-time Olympic team event medallist, was the star of the two-day Dusseldorf Masters.
He featured alongside 16 players who all live or train in the western German city.
Local authorities approved their strict safety and hygiene concept with no spectators, no change of ends, no post-match handshakes, and a frequent change of balls which were all disinfected.
It follows similar small events in tennis in the country where the Bundesliga was the first major football league to resume action.
The basketball top flight is also to follow on the weekend.
Rosskopf said that he wants to give his players some additional motivation as uncertainty remains when regular tournaments can be played again.
“The lads are physically fit. But to do nothing else but training is mentally too demanding in the long run,” Rosskopf said.
Boll said he was happy to play as it “was about time I got some adrenaline going again.”
The tournament in Dusseldorf continues every week for the next three months.
But players could change, although most of them are in the national team or play in or near the city.