If this is a TOP LOADING Roper washer, a no spin problem can have several causes. However, most commonly, this is caused by either a lid switch malfunction or a broken motor coupling. The following link explains how you can diagnose the problem and repair it yourself:http://www.fixya.com/support/r3965207-whirlpool_top_loader_no_spin_problem
If this just a simple matter of the agitator not working, but everything else does, you may just have a worn agitator cam assembly, worn agitator dogs, loose agitator bolt, or all of the above. The following link explains what agitator dogs are and how to access them:http://www.fixya.com/support/r3608577-replacing_agitator_dogs
Whirlpool manufactured washers (such as Roper) use a split agitator design. The top half is known as the "auger, while the lower half is the agitator. Between the two pieces is a cam assembly, with small teflon teeth known as "dogs". There's also an agitator bolt that holds the entire assembly to the center post.
If the auger (top half of the agitator) is slipping, I would suspect the dogs or cam assembly need to be replaced. The part number for the dogs is included in the link I provided. For a little more you can purchase the entire cam assembly which includes the dogs, the cam, the cam seal and thrust bearing.
If the entire agitator appears loose or slipping, check the agitator bolt to ensure it is tight. DO NOT overtighten as this can restrict movement of the agitator or damage it. Tighten until snug.
Replacement parts (if required) can be purchased at any of the following websites:
All these sites are reputable and offer great service with competitive pricing, so shop and compare. The first three sites I listed also include helpful exploded view parts diagrams to assist you in locating and properly identifying the parts you need. If you do not wish to order parts on line, use the part numbers from the Sears website and go to your nearest appliance parts retailer. All these parts are commonly sold as part of their in-store inventory.
If you have any questions, please post back and let me know. I hope this helps you.
NOTE: Roper is manufactured by Whirlpool, so these instructions do apply.