Chelsea forward Romelu Lukaku, center, celebrates with teammates after scoring the decisive goal in the 89th minute of play during a 2-1 exhibition victory over Roma before 25,615 at RFK Stadium. (Paul J. Richards/AFP via Getty Images)

There are two primary seasons for American soccer. The MLS campaign spans from early spring to late autumn. In between, to satisfy a diverse audience, international tournaments and club friendlies flood the landscape. Promoters transform NFL and MLB venues into imperfect stages, and European glitter enhances conventional pitches.

Like the final weekend at a mountain resort, the last guests are packing up, leaving year-round residents to resume their rhythms.

As a 12-week period of some 80 non-MLS matches nationwide neared the end, RFK Stadium, home to D.C. United, welcomed a pair of well-heeled visitors Saturday night.

Roma capitalized on Chelsea goalkeeper Mark Schwarzer’s dreadful mistake in the first half, but veteran midfielder Frank Lampard equalized early in the second and Belgian forward Romelu Lukaku struck in the 89th minute as the Blues claimed a 2-1 victory before 25,615.

Chelsea broke the deadlock when Eden Hazard, a stylish Belgian winger, scampered along the end line with brilliant footwork and connected with Demba Ba, who laid off to Lukaku, 20, for a deflected one-timer.

“There was more energy to us in the second half,” said Lampard, 35, who was among eight field players to enter in the first 13 minutes after the break and turn the match in Chelsea’s favor.

Lampard, in his 13th season with the Blues, is in the process of returning from an Achilles’ tendon injury and sought a good run in the four-game tour finale.

“I tried to inject a little bit of something,” he said. “It’s good for me, for my personal fitness anyway. No point in coming in and just trotting around midfield trying to play easy balls. You have to try to extend yourself.”

American midfielder Michael Bradley, entering his eighth season on the European circuit, played all 90 minutes for Roma, which completed its tour with two victories and a defeat.

Despite the loss, “there were still a lot of good things, a lot of things to build on,” he said. “Up to this point, the work has been very good, and now we head back to Rome” to prepare for the Serie A opener Aug. 25 at Livorno.

Primed to challenge Manchester United and Manchester City, Chelsea will launch its Premier League campaign next Sunday against Hull City at London’s Stamford Bridge.

Roma went ahead on Schwarzer’s howler in the 21st minute. The 40-year-old Australian — in his 23rd pro season and first with Chelsea after moving from crosstown Fulham — misplayed Ryan Bertrand’s routine back pass.

The ball skipped past his foot and hit the left post. As he turned in horror, the ball caromed back between his legs. Erik Lamela took advantage of the mess at the edge of the goal line.

The sequence was eerily similar to the U.S. national team’s second goal against Germany during a June 2 friendly at RFK: Marc-Andre ter Stegen botched a back pass, resulting in an own goal.

Schwarzer redeemed himself to some extent in the 35th minute, diving to his right to stop Pablo Osvaldo’s low drive. Andre Schurrle’s bid for an equalizer just before the half curled just over the crossbar.

Morgan de Sanctis preserved the lead with a reaction save on John Terry’s six-yard header off Schurrle’s free kick. But Lampard equalized in the 61st minute, accepting Ba’s pass and ripping a 25-yard drive to the lower left corner.

Roma tried to answer, but reserve goalkeeper Jamal Blackman, 19, denied Osvaldo’s header with a sensational leaping touch.

“We have had a really good strong preseason — lots of games, lots of training. The team grew together,” Lampard said. “We will be ready next week.”