It was Ireland who started confidently on Saturday, and they almost took the lead when Luke Madeley’s effort from a penalty corner went just wide.
Slightly against the run of play, Great Britain took the lead in the 12th minute with a wonderful strike from Croft on his debut.
He controlled the ball just inside the circle and fired it low past Irish goalkeeper Davy Harte.
Roper’s reverse stick shot early in the second quarter doubled the advantage for the home team.
Ireland got themselves back into the game with a classy finish from Walker. He beautifully trapped a ball into the circle from Jonny Lynch, turned, and poked it past James Mazarelo.
However, seconds after the restart Jonny McKee received a 10-minute yellow card and Great Britain took full advantage when Ward, on his 200th international appearance for GB and England, deflected the ball into the net at the back post.
His second goal came early in the third quarter from a penalty corner that killed the game as a contest.
An excellent team performance from Great Britain was completed near the end when another debutant, Welshman Gareth Furlong, converted another penalty corner routine.
Elizabeth Yeager opened the scoring for the US but Lily Owsley levelled for GB’s women before half-time.
Grace Balsdon and Fiona Crackles scored after the break to give GB a two-goal advantage.
Sophia Gladieux pulled one back via a field goal in the fourth quarter, but the hosts held on for a first win in five games to pull away from the US at the foot of the table, although they remain second-bottom.