FCC Cs3C60 can be driven to a bulk superconducting state without symmetry change by the application of pressure. Its Tc passes through a maximum of 35 K at 6 kbar. We have been recently successful in isolating the isostructural RbxCs3-xC60 family of materials with 0<x<1 in which the effect of physical pressure is mimicked by the application of chemical pressure through isovalent substitution of Cs+ by Rb+. With this proposal, we want to address the nature of the electronic states of the fcc Cs3-xRbxC60 phases at ambient pressure as we cross the metal/superconductor-insulator boundary and traverse the superconductivity dome. We will search for the emergence of magnetism at the insulator-to-metal crossover by using the muSR technique in its ZF/LF variants and characterise the superconducting state for the metallic phases by using TF-muSR.