Romania, who have not reached the World Cup finals since 1998, host Estonia in their final qualifier on Tuesday while Turkey take on the Dutch in Istanbul.
"It was a difficult beginning but we managed to score before halftime and it was a relief for us," Keseru told TVR.
"I am extremely happy because it was my first match and my first goal. I am sure that Netherlands will beat Turkey and we'll beat Estonia to reach the playoffs."
Keseru put the visitors ahead when he headed in Bogdan Stanciu's cross three minutes before the break and Stanciu doubled the advantage from close range eight minutes after the interval.
Gabriel Torje then put the victory beyond doubt midway through the second half, converting a penalty awarded for a foul on defender Vlad Chiriches by Adrian Rodrigues.
Costin Lazar completed the rout with a firm header seven minutes from time with the lively Torje turning provider.