Spurs won 3-0 on Wednesday night as Joao Palhinha, an own goal from Doncaster defender Jay McGrath and a late Brennan Johnson strike were the goalscorers.
Frank said afterwards: "First and foremost, happy with the win, happy with the clean sheet and happy that we are through to the next round. That was the aim. I think the first half was good. Controlled the game, created chances that we wanted and needed. I think we could have scored more goals in the first half actually. Got some big opportunities to Mathys Tel, Rodri and a few other situations that were dangerous.
"Second half was more disjointed. I think we threw the ball away too easily. The pressure was not top but also praise to Doncaster. They came very brave, very good to stretch us. So if the pressure is not perfect they made it difficult so praise to them as well."
Tel can improve
Frank was asked about the performance of Mathys Tel and insists he's happy with what he's seeing from the Frenchman.
He stated: "He played striker against West Ham which I think he did quite well. Worked very hard for him to arrive in the right areas which I think he did today. In terms of performance that was a step up.
"Then we can look at the end product to score the goal but the performance to arrive in the box I was very happy with. Just close with the first ball from Brennan, ready for the cutback. Second half got in there on two other good situations and had a nice shot. I think it was a step up in terms of performance.
"I think you can see that his ability in this game to arrive in the box and the pace he got to both running behind and also getting into the right areas, I think it's good. I think his pressing ability is very good. I like the way he works in that situation.
"And then I think his link-up play is something that is a good level, but he can be even better."