Henshaw, 21, and Marmion, 22, have both found themselves in Ireland boss Joe Schmidt's plans after clocking up almost 800 minutes on the field between them so far this season.
And, while Lam knows his squad can't compete in numbers with some of the other GUINNESS PRO12 sides, he is keen to ensure his side are producing quality youngsters who can carry the Connacht baton.
"We've got the smallest squad depth of all the GUINNESS PRO12 teams. One thing that is vital in this long competition is squad depth," Lam told the Irish Times.
"We have to rely very heavily on the young guys. Our playing budget as well. You get injuries which really hit us.
"The key focus is to make sure our systems are world-class because we are fast-tracking guys, guys are getting opportunities from the academy.
"Look at Robbie and Kieran, look at how young they are, but remember they have now played three seasons of week-in-week-out rugby.
"There are not like other 21-year-olds who are playing occasionally for their club, maybe played four or five games off the bench.
"These guys nearly have 70 caps for Connacht. Now Robbie is building his internationals caps, and with that comes experience."
Follow us on Facebook, join the conversation on Twitter, sign up to our YouTube channel for extensive match highlights and sign up for our newsletter for regular updates on the GUINNESS PRO12
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland