This study concerns the use of rheology to obtain quantitative information on the microstructure of polyolefin-based materials. Such properties have crucial implications along both directions of the chain-of knowledge of polymeric materials. Moving backwards, in the direction of polymer synthesis, rheology can link the material response to the details of the molecular architecture. Moving forwards, in the direction of technological applications, rheology can provide a relevant link to the processing as well as to the final material properties. Determining the molecular structure of polyolefin-based materials is a relevant scientific and technological challenge. Molecular weight, its distribution, and structural details are often difficult to ascertain for industrial polymers. We attempt to address this challenge starting from the linear rheological response of polyolefins evaluated over the largest possible frequency range. To this end, linear rheology is measured in concentrated, entangled solutions, instead of melts, thus overcoming some intrinsic experimental difficulties encountered in measuring the latter. A time-concentration superposition principle is then applied to obtain rheological master curves. Molecular models and constitutive equations for entangled solutions are used to extract the quantitatively relevant microstructural information.