ROSEBURG, Ore. — When President Barack Obama arrives here Friday, he will find a timber town still in mourning over the shooting that killed eight community college students and a teacher. But he will also find another deeply held emotion — seething anger over his calls for new gun restrictions. Only a week after a gunman strode into a writing class and opened fire on classmates, many people in the region known as Oregon’s Bible Belt are quick to reaffirm their opposition to stricter gun laws.