Is a gate resistor needed on a 2n7000 mosfet when driven by a 4543 BCD for multiplexed led display?
I really wouldn't worry about it with only 10mA being switched. The output resistance of the 4543 will prevent any tendency for common-drain oscillation. 

Just make sure you have a reasonable bypass capacitor (10n to 100n) on the 4543 supply and make the layout halfway decent and you'll be fine.

Using a relatively large value (like 10K) would slightly reduce EMC by making the transistors switch more slowly, but unless this is a display for a very sensitive instrument it's not going to be all that important. It might also cause you some problems with 'ghosting' that could require code changes.