The Portuguese boss, who was sacked by the Blues after just nine months in charge, has taken the reins at White Hart Lane following the exit of Harry Redknapp in the summer.
"It is early days but when you hear him interviewed he's dour, there is no happiness in his voice," the Daily Star quotes Roberts as saying.
"As a manager you have to pick up the boys. He needs to get a personality change. You might say that is the way he is but you've also got to be happy sometimes and that breeds confidence in the lads so that they play better.
"To me it doesn't look as if he has learned from his time at Chelsea when he spoke badly to some players."