Elden Ring - Rogier quest not advancing to "About the corpse under Stormveil" fix [Xbox 4K HDR]

So I am going through guides on the internet to try and get the Spellblade set for my mage. The guides say that once I touch the bloodstain at the bottom level of Stormveil, I can then come back to Rogier to talk to him and a dialogue will come up saying "About the corpse under Stormveil". This did not work for me.

So it turns out that I have to kill this huge boss called "Root Monster" before the bloodstain before I touch it. Unfortunately this boss is incredibly hard to kill - you cannot summon anyone to help you, the area is super confined so you get cornered easily with nowhere to run, and the boss is huge while dealing insane damage.

So the only way to kill the root monster is basically by going to a high ground where he can't touch you and shoot things down at him. In this video you will see how to do that as well. Once you have defeated him, touching the bloodstain and then going back to Rogier will get you the next dialogue option.

Unfortunately the next part of the quest is super hard - you have to head to Black knife catacombs to fetch the black knife print, which is dropped by one of the two bosses (the harder one) in the catacombs. I managed to defeat the easier boss but still yet to find out how to defeat the harder one. More on this later!