Jefferson Farfan and Max Meyer were on the scoresheet at the Veltins-Arena in Gelsenkirchen as Schalke continued their fine form to move four points clear in fourth in the Bundesliga.
With Borussia Monchengladbach losing a third straight game on Friday, Schalke's place in the final UEFA Champions League place looks safe for now.
It came thanks to a first half that drew praise from Keller, delighted by his side's tactical execution.
"We played an almost perfect first half. The team dominated play, refused to let the Hanoverians into the match and kept their two danger men under control," he said.
"Tactically, we did exactly what we set out to do; our quick switching and work down the wings made us a threat throughout and led to two fantastic goals from Jefferson Farfan and Max Meyer.
"Klaas-Jan Huntelaar and Kevin-Prince Boateng also had great chances to score."
Farfan finished off the easiest of chances, tapping into an open goal on 39 minutes after Sead Kolasinac's fantastic run down the left.
Meyer struck a minute before the break after a fine team move, sweeping Atsuto Uchida's cross in to make it 2-0.
Keller was pleased his team gave Hannover few chances in the second half as the visitors looked to attack.
"We knew Hannover would try everything in the second half and attack us even earlier but, apart from Mame Diouf's chance, we kept our defence tight after half-time," he said.
"Huge compliments must go to my team; they performed brilliantly for the third match in succession."
Roman Neustadter and Uchida failed to finish the game for Schalke due to injury, while Benedikt Howedes faces up to another month on the sidelines with 'torn muscle fibres'.
Meanwhile, Hannover coach Tayfun Korkut said his 10th-placed team would move on quickly from the loss.
"We came to Schalke with confidence after two wins against Wolfsburg and Borussia Monchengladbach and wanted to continue to play as we did in those games," he said.
"However, the defeat isn't a setback for me or the team."
