Designing a bluetooth 4 low energy device - what needs to be taken into account for future FCC and CE certifications
A shield is required for a modular device (All the RF modules with FCC certification have a shield). A non modular device, under FCC 15.245 or 15.247 (2.4GHz ISM regulations) does not require a shield, however, a shield will generally improve your performance (better SNR and noise immunity). Also, transceiver modules under FCC require a voltage regulator of some sort.

Modular in this context means that the transceiver can be assembled or replaced by the end user (easily soldered or connectorized module).