Saurabh knew about Shiv rotating his hands, but he did not speak anything because he did not wanted to be disqualified, but played a MASTERSTROKE where he made Shiv quit the game inorder to be portrayed as being generous and how they respect women.Saurabh always wants to win the trust of housemates and he did succeed in that which is why no one questioned him when Deepak accused him of giving him promise that, he will not reveal the truth to anyone. Everyone believed him and he took advantage of that, he conveniently putted the entire blame on Deepak and had the audacity to lie infront of him.
Even today, he lied to not remember planning with Shiv and Sreesanth about kicking Deepak, but he was part of that conversation. How conveniently , he wants to put the entire blame in Shiv ,so that, he is still portrayed as the innocent one, but Deepak knows a lot about Saurabh, he knows that Saurabh is very cunning and he has a very disrespectful sense of humour for the housemates. Saurabh pretends to be decent, but in reality, he passes double meaning jokes and even Deepak said how he uses worse words than sala.
He got embarrassed and could not say anything out of guilt because he truly got exposed and had no justification for that, he wanted to take revenge from Deepak revealing his truth,so he just threw Shiv under the bus , so that, the blame will only go to Shiv and he will be held responsible for that.
Saurabh is involved in playing politics, but he pretends to be a clean person which he is not. He listens to conversations like Urvashi and informs the person who is being talked about like he informed Dipika in one of the episodes when the housemates were influencing neha against Dipika, he does idhar ki udhar and udhar ki idhar in such a subtle way.