Scarlets duo Jonathan Davies and Scott Williams have impressed in the heart of midfield when given their chance while Roberts is certain to make the trip to New Zealand so it's imperative Henson produces the goods against England this afternoon to state his case.
"Gavin needs to make good decisions," said Howley. "We have a lot of competition and I think that brings out the best of players personally.
"Selection is an on-going process which has gone on over the last two months and we have tried to gain continuity.
"Gavin and Jamie Roberts have the chance to show their partnership. I thought Jon Davies played very well last week against England and he provides us with a left-footed kicking option.
"The impact of Scott Williams in the last two months should also not be underestimated. We have been very impressed with his performances from the bench."
Henson will line up alongside Roberts for only the second time but the duo go into the game with Howley giving them a license to thrill.
"Gavin can kick, pass and run, while you have the physicality of Jamie Roberts. We tried that combination against Italy in 2009, but we did not have the quality of possession that day.
"We are hoping to get more against England."
Wales v England, Millennium Stadium, Sat 13 Aug, KO 2.30pm
Wales James Hook; George North, Jamie Roberts, Gavin Henson, Shane Williams; Rhys Priestland, Mike Phillips; Paul James, Lloyd Burns, Craig Mitchell, Luke Charteris, Alun Wyn Jones, Dan Lydiate, Sam Warburton (Capt), Toby Faletau.
Replacements: Huw Bennett, Ryan Bevington, Josh Turnbull, Justin Tipuric, Tavis Knoyle, Scott Williams, Aled Brew.
England: Ben Foden; Chris Ashton; Mike Tindall (Capt), Shontayne Hape, Mark Cueto, Toby Flood, Richard Wigglesworth; Alex Corbisiero, Steve Thompson, Dan Cole, L Deacon, Courtney Lawes, T Wood, H Fourie, N Easter.
Replacements: Lee Mears, Matt Stevens, Tom Palmer, James Haskell, Danny Care, Charlie Hodgson, Matt Banahan
Referee: Alain Rolland (Ireland).