Here are some of the stamps and rollers that I use to decorate my handbuilt pieces. Some of the longer rollers were extruded, and then carved. Most were cut from thick cylinders thown on the wheel. If you allow the cylinders to stiffen for a couple of hours, you can easily cut nice even sections with your off-the-hump cutting thread.
Any clay will do - these are mostly my cone 10 salt clay, but others are lowfire clay. Stamps can be carved from prepared blocks of clay that are are just still dry enough to carve - don't try to make them with softer clay or your impressions will not be crisp. I bisque fire them when dry, and roll them by hand to make impressions. I've thought about making wood handles for them but is easy to use them by hand.