...And be careful to keep the strip out of any wet ink, like a damp print or the sponge/capping stations. It's best to remove the strip by unhooking the spring on the left of the strip (turn the machine off before doing this). Next, use the capping station wrench to lower the caps, and slide the head to the left. Unscrew the locking tab on the right side (do not remove the screw totally). Clean the strip thoroughly with alcohol--99% works best.
To reinstall the strip, move the head back to the right. Insert the strip (right side up, you can tell which way is up by looking at the hole on the right side of the strip. It should be on the bottom.) Insert about half of the strip into the channel. Then slide the head over to the left, over where you have inserted the strip. Now, carefully push the strip to the right and insert the remaining section. Lock the strip into place by tightening the screw on the tab to the right. Now, reattach the spring on the left. Finally, move the head all the way to the left side of the machine, checking that the strip moves freely inside the encoder strip sensor. You can now turn the machine back on. As mentioned above, do an environmental match on Pro II and older machines. Pro III's will do one automatically. This is the procedure for a Pro III, but is essentially the same for all Rolands.
TIP: If your encoder strip becomes too dirty to clean, scratched, or otherwise damaged to the point it cannot be read by the sensor, you can turn it over and use the bottom! Just remove the flange from the left side, attach it to the right side and reinstall.