The microscopic Polymer Reference Interaction Site Model (PRISM) theory has been generalized and applied to study dense solutions and melts of polymer tethered spherical particles. Intermolecular pair correlation functions, collective structure factors, and bulk moduli are calculated to understand the equilibrium organization and tendency to microphase separate. The complex interplay of entropy (translational, conformational and packing) and enthalpy (monomer-particle attraction) leads to different spatial arrangements with distinctive scattering signatures, and a rich phase behavior. For melts of these tethered particles, at low monomer-particle cohesive strengths the particles experience depletion attraction. As the monomer-particle attraction is increased strong polymer mediated bridging of particle cores is observed. The location of the peaks in the structure factors suggest that these tethered particles prefer to organize themselves in a specific geometry that is dictated by the subtle competition of depletion attraction, osmotic repulsion, monomer adsorption and grafting constraints. The effect of the length of tethered chains, number of tethered polymers per particle, core radius, total fluid packing fraction, and monomer-particle interfacial attraction strength on the statistical structure, properties and phase behavior will be discussed.