First and foremost, check the laws and regulations for TX. You may not be able to bring back Orconectes rusticus, as it's a highly invasive species in some areas. Usually, any qualms are usually seen within the sale of this species, and usually it's prohibited. But still, better to check all avenues before hand.
Anyway, O. rusticus is a fairly easy crayfish to keep...
They can handle a wide variety of temperatures as they are found far North and far South, but for the basic aquarium aim for between 65-75 for good activity and health.
They are a large and aggressive species, so care should be taken in setting up a proper aquarium. If you are keeping multiples, provide a good amount of space for each (general rule of thumb is 10gal per crayfish) and remember that they utilize primarily the floor space. So tall tanks may be large, but to a crayfish they're small and don't provide a lot of moving space. Provide plenty of cover and hiding spots for them. And if possible, try to keep more females than males (male/male fighting will be lessened greatly this way and allow for more overlap in individual territories).
It's not recommended that you keep them with any fish or aquatic life that you don't want to see become a snack at some point. Even well fed Rusties will occasionally feel inclined to hunt, and hungry Rusties will treat any tankmates like a buffet waiting to happen.
They will eat almost anything you give them and aren't very fussy. Just make sure you giving them a variety of meat and vegetable matter, and a good source of calcium (crushed egg shells, cuttle bone, etc) to ensure they're getting all their necessary nutrients.
Other than that, enjoy. Rusties turn into some big monsters and are really awesome crayfish. Oh, keep in mind though... you can NEVER release this crayfish species and it should not be used as bait because of the invasive issues it's already causing. Unwanted Rusties should be given to new homes, humanely destroyed or used as food (like you said, for your Oscar).