Roger and Voldemort were absolute enemies in Voldemort's eyes.
Voldemort wanted to obtain the eternal, supreme power he envisioned, and a "monster" like Roger, who posed such an enormous threat, had to be eliminated.
As for Roger, Voldemort had a blood feud with his partner, and his very existence also threatened Dumbledore, to whom Roger owed a great debt of gratitude.
Besides, Voldemort was hardly as innocent as a baby.
So although Roger did not consider Voldemort a personal nemesis, if the opportunity arose, he would not mind erasing him from the world.
But whether it was Voldemort or Roger, neither of them was particularly fussy about such things.
Even if the other was an enemy, they did not mind talking and learning from one another, gaining knowledge that could make themselves stronger.
They had no notion of dismissing someone else's achievements simply for the sake of so-called political correctness, even when an enemy's weapons were highly useful.
Learning the barbarians' superior techniques to subdue the barbarians was utterly ordinary to the two of them.
Thus, when Roger knew only of Voldemort's five Horcruxes, and Voldemort was constrained by an oath and other restrictions that prevented him from acting against Roger at school this year, leaving neither able to do anything to the other, the two still exchanged ideas from time to time.
December 24th, Christmas Eve.
As usual, Voldemort and Quirrell came to their appointment, continuing that game Roger had almost no chance of winning.
"Don't you find it ironic?"
"Hm?" Standing before the Room of Requirement, which could only be entered after passing it three times, Roger turned to glance at Voldemort as he paced back and forth to open the room.
Using Quirrell's body, Voldemort flicked a plastic bauble hanging beside the tapestry of Barnabas the Barmy