As a result of the medial ligament problem, 25-year-old Roberts will miss Wales' next match with Italy on March 10 but will hope to return for the clash with France at the Millennium Stadium a week later.
"We are hopeful that Jamie will be fit for our final game against France," Howley told the Guardian.
"He was clearly not right after taking a knock and he gave away two penalties for offside, which is not like him."
But Howley believes Wales, who secured the Triple Crown at Twickenham and remain on course for their third Grand Slam in eight years, have already displayed their strength in depth with their victories over Ireland, Scotland and England.
Against Ireland, Wales lost captain Sam Warburton at half-time while flying winger George North limped of after 40 minutes against Scotland, and Howley believes the RBS 6 Nations leaders can cope with Roberts' absence.
"It shows the maturity of the side that we are able to overcome such injuries," added Howley. "We were not at our best against England but it was always going to be a game where the result was everything.
"The media hype before the game was that we were going to win at a canter, but that was never going to happen. The history of the fixture told you that and we knew England would be tough to crack.
"It is all about building blocks. We cannot afford to get ahead of ourselves and that means having a next game mentality."