EDIT: This is basically manslaughter. While he did not conspire to murder, his actions resulted in one. I think it's the same if, drinking and driving, you accidentally kill someone -- while there is no malicious intent, your idiocy resulted in someone's death. Arguably, however, this punishment may be disproportionate. I bet the state's appellate lawyers are busy.
ahahahaha so lemme get this straight.
My roommate asks me to borrow a bedsheet (he can either tell me it is for some normal purpose like SLEEPING, or I can simply not ask) and I give it to him. While I am off at class on campus 1.5 miles away, my roommate gets some girl to come over the apartment and strangles her with the bedsheet until she chokes and dies.
Although in this case the item lent is
directly the weapon of death, all of the other circumstances you described are the same. By lending the bedsheet, I did not conspire to murder, but my roommate's actions resulted in a murder. I had no malicious intent. I was not at the crime scene. My
idiocy of lending my roommate the bedsheet resulted in someone's death.
OOPS GUESS ITS MANSLAUGHTER