If Roglic had more in the tank he should do that, because it could be important for him to test or "simulate" the style of race/ way the Tour has been raced in the last 2 years.
He should push himself everyday to the limit, to test himself, check his power numbers and see if he can go full gas everyday, and put minutes in this competition.
There will be no trains or defensive cycling in the Tour with Pogacar and Vingegaard there. Looking at the gaps, day and day out Vingegaard and Pogacar will be 2/3 minutes at the front against this competition Roglic had, so it could be interesting Roglic trying something similar, to "simulate" the conditions of the way the Tour will be raced, and see where it takes for him.
The way they raced today and yesterday, by Roglic and Bora, will not work when the other two go full gas. There's no place to hide.