I have a room mate who has decided no to renew her part of the lease for the next year. Her lease ends August 1st and after that I am the sole leaseholder. Do I have the right to make sure she has to leave by or on that day? I won't go into the personal reasons, but I want her gone asap... after August 1st she's not on the lease. Can I get her for trespassing if she refuses to go? I'm in Indiana, if that matters.

After August 1st, if she is still there, you should be able to sue her to evict her. It doesn't appear that you need to serve her an eviction notice (or "notice to quit") prior to such suit because of the following Indiana statute:

"IC 32-31-1-8
Notice to quit; when not necessary
Sec. 8. Notice is not required to terminate a lease in the following situations:
(1) The landlord agrees to rent the premises to the tenant for a specified period of time.
(2) The time for the determination of the tenancy is specified in the contract.
(3) A tenant at will commits waste.
(4) The tenant is a tenant at sufferance.
(5) The express terms of the contract require the tenant to pay the rent in advance, and the tenant refuses or neglects to pay the rent in advance.
(6) The landlord-tenant relationship does not exist."

Actually I don't think you can do anything. You are both signed on the lease with your landlord, correct? In which case you have no rights to do anything, only the landlord has. However, if you are her landlord, than yes you can force her to leave.