Why does Roderick go to the narrator's room near the end of the story?

Roderick goes to the narrator's room in order to show him the storm.

“And you have not seen it?” he said abruptly, after having stared about him for some moments in silence — “you have not then seen it? — but, stay! you shall.” Thus speaking, and having carefully shaded his lamp, he hurried to one of the gigantic casements, and threw it freely open to the storm.

“You must not — you shall not behold this!” said I, shudderingly, to Usher, as I led him, with a gentle violence, from the window to a seat. “These appearances, which bewilder you, are merely electrical phenomena not uncommon — or it may be that they have their ghastly origin in the rank miasma of the [page 97:] tarn. Let us close this casement — the air is chilling and dangerous to your frame.