The 54-year-old German, who took Hertha Berlin from the Bundesliga's Second Division in to the Champions League, met Romanov in Lithuania on Friday.
But Rober told the Sunday Mail why he has become the third coach after Motherwell boss Mark McGhee and Slovakian Vladimir Weiss, to knock back the chance to move to Gorgie.
"He has some good ideas for the club.
"But the trouble was I have my opinions on how to coach and he has his ideas.
"Unfortunately these ideas would not come together.
"He has different ideas on how to move a club forward. He is a businessman and I understand why he wants what he wants.
"But I have been 35 years in professional football.
"Don't get me wrong, I am not saying anything bad about Mr Romanov and as I said, I was impressed by him.
"But I had this feeling that we couldn't come together."