The sentences given do not have the underlined parts.
Anyway, when we say independent clause, this is the clause that conveys a complete thought. It consists of the subject and the predicate. In other words, it is a simple sentence. On the other hand, a dependent clause is a clause that do not convey a complete idea. It needs the independent clause to make it understandable. Here are the answers:
1. Many people use bamboo screens : INDEPENDENT
that roll up and down : DEPENDENT
2. Bamboo is the fastest growing plant : INDEPENDENT
that we know : DEPENDENT