You are performing SELECT and you are getting "unable to extend rollback segment"? That sounds quite impossible! Can you give us some more detail about your problem? Does your select use some user created functions that might be writting something to the database?

And BTW, the number of columns you are selecting has practicaly no influence on the execution time of your query. You select 1 or 10 or 150 columns - the execution time will be (roughly) the same.