Rose has missed Tottenham's last 10 games due to a toe injury he suffered against Tromso in the Europa League.
Right-footed Kyle Naughton originally deputised for Rose at left-back, but Vertonghen has started there in the last three Barclays Premier League games.
Vertonghen, who is left-footed, gave an interview last week in which he stated that he preferred playing at centre-back, even though he regularly plays out wide for the Belgium national team.
But with Rose set to be out until after the international break, Vertonghen looks like he will have to remain out of position for the time being.
"I have had lots of conversations with Jan regarding this situation," the Tottenham manager said.
"Unfortunately he has to sacrifice his position as centre-back for the team.
"His position at centre-back is not in question. He is one of the greatest central defenders I have worked with. He knows that and he knows that position is waiting for him whenever we have options at left-back. He has my word.
"He hasn't fallen in love (with playing at left-back). I know he doesn't like it, but it's no big deal.
"It's a decision I have to make for the best of the team."
Although Vertonghen does not like playing at full-back, he is more than an able deputy to Rose.
The graceful Belgian is capable of making dangerous attacking runs to support the midfield, he has a keen eye for a pass and his crossing is also good.
The fact that he regularly plays in that position for his national side also gives Villas-Boas confidence that the 26-year-old can perform well there.
"Funnily enough I told Jan I would be the first person on the phone to him when he goes to the World Cup and plays left-back," Villas-Boas said with a rare smile in what was otherwise a very tense press conference to preview Tottenham's Europa League game against Sheriff Tiraspol on Thursday night.
Tottenham's manager lashed out at those who criticised his decision to leave Hugo Lloris on the field of play after the goalkeeper was knocked unconscious by Romelu Lukaku's knee at Goodison Park.
The Portuguese also criticised Everton striker Lukaku for not apologising to Lloris over the collision, which he thinks was avoidable.
"I'm disappointed that Lukaku hasn't contacted Hugo," the Spurs boss said.
"I don't question Lukaku's integrity or human side. I have maximum respect for him and I think he has for me.
"I don't want to question Lukaku, he's a young player, wonderfully gifted but I think he could have jumped over Lloris."