Both forwards are ruled out of club action in the short term but should be able to take their places in the Lions squad, who play their first game against Argentina in Cardiff on May 23.
Prop Rowntree and flanker Moody both suffered knee injuries in Leicester's Heineken Cup semi-final defeat by Toulouse on Sunday.
Rowntree, who limped off in the first half, had a scan on Monday which revealed no serious damage and the Tigers hope he will be able to play in the Zurich Premiership final - if they qualify - on May 14.
Head coach John Wells told the club's official website, www.leicestertigers.com: "Graham damaged synovial tissue in his knee, which has filled the joint with fluid.
"He has had his knee drained and there is no ligament or bone damage."
Moody has a medial ligament strain, which could keep him out from either two to three weeks or four to five weeks.
"We're obviously hoping for the former," said Wells. "We will know the severity of his injury in the next few days, but at this stage we think he'll be out for two to three weeks."