As was mentioned in the previous post, Roderick suffers from a severe mental illness, but there is indeed an unknown "superstitious" force that keeps him inside the home. Roderick has physical ailments that prevent him from leaving the house, such as sensitivity to light and sound, but there is also something more foreboding and ominous in nature keeping him secluded in the house. Although Poe does not go into specific detail, he mentions that Roderick was "enchained" by "certain superstitious impressions" which is why he refuses to leave home. Roderick, Madeline, and the house share some sort of common spiritual connection and are inextricably linked. Roderick's depressed, grief-stricken personality coincides with the gloomy nature of his residence. Roderick is also the last male heir of the Usher family, and upon his death, the house collapses. Roderick and the house are one, and his well-being is linked to the home by an unknown spiritual force which prevents him from leaving.
As mentioned above, there does indeed seem to be a loadstone that draws Roderick to the edges of insanity, something pulling him, unnerving him in the house. That he and his sister are unnaturally connected is suggested in Poe's story; she has the physical infirmity while he has the mental. Roderick and Madeline are not complete without the other; he cannot leave with his sister there.
We are told that it is part of his nervous condition, that forces him to seek solitude and rest. However, behind this, I think we can infer that there is some kind of compulsion that keeps him there. He clearly does not like the house and considers being the heir of the house of Usher a curse. It is suggested that he, Madeline and the house all are tied together somehow. Note how the house is destroyed when the two heirs die.