The pair joined Gatland, Andy Farrell and Andy Irvine in picking a provisional squad in Edinburgh earlier this month and they know it's an area of their preparation they simply have to get right if they are to topple the Wallabies in their own backyard.
The first two weeks that we get together is obviously the time to establish a style of play. For four countries to come together
"The one thing we have to get right over the next three or four months is selection," said Howley, who knows the importance of picking both the right initial squad and then the right Test team.
"The key to international games, and particularly with the Lions, is getting selection right.
"We all talk about form and confidence and we talk about class. We lost the series in 2009 so we obviously got selection wrong. Ultimately, that's key to the foundations of the tour.
"Creating a strong foundation is vital and momentum is important with the Lions. The whole focus is obviously on the Test series but the building blocks to that are the midweek games."
December's post-autumn internationals selection meeting took around three hours such is the competition for places from all four Home Unions.
Forwards coach Rowntree admits the discussions were far from straightforward, even with four months still to go before the final call has to be made.
"In my area, the back row options alone took an hour. We're very strong there," said Rowntree.
"That's the beauty of the Home Unions: we've had our disappointments over the past year, particularly in the autumn series, but we've got an exceptional player base.
"We've got some great players that we can choose from and trying to narrow them down to a workable group is going to be a challenge for us.
"But as Rob says, we've got to get it right.
"We haven't won a series since 1997. That's not being negative, it's a fact, and it's a real driving force.
"I think now's probably the best chance we've got of doing it with this group of players. We have to deliver."