If you want to make lots of beads of the same size, a bead roller may be just the tool you need.
Bead rollers are two pieces of plastic with corresponding troughs and grooves. Measure the clay (according to instructions that come with the roller), put the clay into the correct trough, fit the two pieces together, and move the top until the clay conforms to the desired shape.
Available on-line and in the clay section of some craft stores, bead rollers usually allow you to roll two to three shapes or sizes of beads per tool. There are tools that roll different sizes of circles, ovals, bicones, tube beads, and other bead shapes. Making beads on bead rollers takes a little practice-mainly because you need a very specific amount of clay to make each different style of bead-but once the technique is perfected, they make short work of rolling practically perfect beads.
It is also possible to make your own bead rollers from polymer clay, PVC pipe, other plastics, metal, or wood. However, making homemade bead rollers may require more time and experimentation than many are willing to invest.