Observations of bulk plasma rotation in Radio Frequency (RF) heated JET discharges are reported. The study is concentrated on RF heated L mode plasmas. In particular, the toroidal rotation profiles in plasmas heated by Ion Cyclotron Resonance Frequency (ICRF) waves and Lower Hybrid (LH) waves have been analysed. It is the first time that rotation profiles in JET plasmas with LH waves have been measured in dedicated discharges. It is found that the toroidal plasmas rotation in the outer region of the plasmas is in the co-current direction irrespective of the heating scenario. An interesting feature is that the toroidal rotation profile appears to be hollow in many discharges at low plasma current, but a low current in itself does seem not to be a sufficient condition for finding such profiles. A loss of fast ions is one mechanism that could explain hollow rotation profiles. This possibility has been investigated by numerical simulations of the torque on the bulk plasma due to fast ICRF accelerated ions. The obtained torque is used in a transport equation for the toroidal momentum density to estimate the effect on the thermal bulk plasma rotation profile.