Federico Balzaretti and Adem Ljajic scored second-half goals as Garcia's team made it four wins from as many games in the Serie A, moving top.
Garcia wants his team to improve in the first half of matches, but said their efforts in defence were key in overcoming Lazio.
"The most important thing was winning, no doubt about that, but we also managed to put in a good defensive performance," he said.
"The whole team managed to defend. We know that we have many skills that allow us to score goals and this happened in the second half, but I hope that in the future we'll also be able to score a goal in the first half."
Garcia refused to be drawn into title talk after Roma's latest win and said their goal was still to finish in the top five.
"We should not forget that our objective is to finish the season in the top five. Ambition is also a quality, so we'll see if we'll be able to have a great season and achieve more than that," he said.
"As of now, it's too soon to make an accurate forecast."
Garcia paid tribute to his entire squad and praised substitutes Ljajic, Rodrigo Taddei and Marco Borriello for their contributions after coming on.
"We don't win with 11 players, we win with the whole squad - and we also owe thanks to the three guys who came onto the pitch today, just like against Parma," he said.
"As you've said, Taddei was at 100 percent and also Borriello managed to do great things for the team in five minutes.
"I'm sorry he hasn't managed to score a goal because he would have deserved it."
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