Garcia's men claimed all three points at the relegation-threatened side thanks to a 16th-minute strike from Mattia Destro and substitute Michel Bastos' injury-time effort.
But the game was marred by Rizzoli's controversial decision, in which the referee, who will feature at the FIFA World Cup later this year, initially pointed to the spot in the 36th minute after Roma defender Mehdi Benatia appeared to have fouled forward Nicola Sansone.
"It's never easy to win on the road," he said.
"I liked our play until the incident between Benatia and Sansone where Rizzoli made the right call."
Garcia remains hopeful that the capital club, who approached the weekend 14 points behind Serie A leaders Juventus, can win a first Scudetto since 2000-01.
"There's a big gap with Juve," Garcia added.
"But we'll keep going while it's still mathematically possible."
