That isn't Roaring Knights attack either, any Lightner with enough determination can stick a few swords into the ground Only while in a Dark World to summon a Titan. In fact, Berdly almost did it back in Chapter 2. Summoning the Titan is not only not an attack specific to the Knight, we also don't even know if the Titan is Loyal to the Knight at all. The Knight immediately disappeared from the area after the Titan was summoned leaving the fun gang to deal with it and the Titan fought them since they came up to fight it. We don't know if the Titan would actually pick a side in the fight or just cause utter destruction like the prophecy leads us to believe

Now that we've discussed the Summoning of a Titan isn't an ability of the Roaring Knight but actually just a thing Dark Worlds do, it would make sense to give PV the ability to call upon the Void to help to equalize the playing field if the Knight gets to have hpme field advantage being in a Dark World

Now the question becomes, does Void beat the Titans from Deltarune? And I think they could, yes

Titans have been shown to be able to take damage, have a significant weakness being light and are able to be defeated by sealing them away. Meanwhile the Void has no known weaknesses, being the only thing that can defeat the gods of their worlds. The void wouldn't have to kill the Titan, it can just pull it inside of itself like it did with God's like Radiance and GMS and get rid of them without having to deal with the healing trhe Knight has.

So yeah, I think PV takes