The 25-year-old, who has been earmarked for the right-back slot at Deepdale next season, made in excess of 300 appearances for the Hatters having come through the ranks at his hometown club.
North End stuttered to a lower mid-table finish in a disappointing League One campaign last term, but Westley's ambitions stretch far beyond the third tier according to Keane.
"The manager's vision is to get Preston into the Premier League," he told the Lancashire Evening Post. "He has a winning mentality and his aim is to win League One this season.
"During the talks about coming here he spoke about exactly what he wants and expects from his players. All managers do things a little bit differently to each other.
"Graham Westley has his ways and methods, and to be fair they didn't do Stevenage any harm did they? I'm just looking forward to July 3 now when pre-season training starts. It will be a fresh start for many of the squad and hopefully good things will follow on."
