Fraser Thornton will step in as interim chief executive until Stewart and Thelwell are replaced.
“At first, it’s always not nice when some people around you get sacked,” added Rohl.
“I had a good relationship with Kevin, we were always in a daily business. We spoke to each other, with Patrick as well. They were also involved in the process when I arrived here, building up something.
“Kevin and Patrick were in a good relationship, we had always good conversations to each other, we were honest to each other.
“But it’s football. Football is never about the past, it’s always about the future and this is what we have to also understand. We have to move forward and we have to take the situation like it is.”
Rangers are still without a point after four Europa League games, while their Portuguese visitors have nine, including the three they picked up with a win at Celtic.
“They are well organised, they are very aggressive, how they play football against the ball, they have solutions with the ball,” Rohl said.
“They will also come with confidence in this competition, but it’s for us as well, a new challenge, we know we need points in this competition as well.
“I want to see tomorrow a next step forward compared to the last two European games. On this level, every mistake could be a big mistake and I think this is also important in such a game, play without mistakes but play on front foot, bring the crowd behind you, try something instead of being passive and just waiting.
“I think this is what I want to see from my team. Then, let’s see, deliver a proper fight and try to get points.
“I know, if we play on front foot, the supporters were straight there, and I think this is what I want to see. I know, especially in Europe, there’s also opponents, there are also some good players, and this is not always possible, but this is what we have to try to do more.”
