mssql revert changes made today without backup
My Recovery model is set to simple


In short, there is nothing you can do but learn from this lesson that important databases should use the full recovery model (along with proper restore plans).


  Can i use the logfile for this


Since it's in the simple recovery model, most likely not.


  Is 'ROLLBACK' another option ?


Only if the transaction is currently open and it's a single transaction. If it's been committed, nope.