The former Napoli trainer believes his team could still be in with a shout for the Scudetto after its win over Luis Enrique's men left the club six points behind leader AC Milan.
Goals from Hernanes and Stefano Mauri were enough to give the Biancoceleste all three points against their bitter rival which had Maarten Stekelenburg sent off after only seven minutes.
The result means Reja's men are now in third place, six points behind leader AC Milan, and the former Napoli coach believes his team could still be in with a shout for the Scudetto.
"At Lazio, we have everything to play for in the league, we must keep believing. We need to keep chasing Milan and see if they lose matches," he told Lazio Style Radio. "I want you to recognize the values of this team. We must always go on to the field to win. Now, let's enjoy this, but even with Bologna next, it will be tough and that is followed by facing the revelation of the season, Catania.
"We have to think about doing the best we can, achieving the maximum, then if we do not win, it is only because the opponent is better than us."
The victory over Luis Enrique's side meant Lazio has recorded two league victories over Roma this campaign, the first time the team has done so in 15 seasons.
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