In order to improve the mechanical properties of polymer composites, natural fibers are being employed more and more as reinforcements. However, incorporating natural fibers can be difficult in rotational molding, a process used to make hollow plastic objects like kayaks and fuel tanks. Bi-axial rotation is a procedure that can result in fiber aggregation and is challenging to regulate. The optimal combination of NaOH-treated peanut shell powder (TPSP) and linear low-density polyethylene (LLDPE) for rotational molding was examined in our research reported in the manuscript. Processability was assessed using a variety of testing techniques, such as Fourier transform infrared spectroscopy (FTIR), particle size distribution, bulk density, melt flow index (MFI), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). Significant peaks with TPSP concentrations in LLDPE ranging from 10 to 22% were shown by the FTIR. Blends of TPSP with LLDPE containing more than 18% TPSP were not acceptable for rotational molding due to poor flowability, as shown by particle size and bulk density investigations and supported by MFI data. According to our study, a 16% TPSP blend was the best formulation for rotational molding since it improved the thermal stability and increased the crystallinity by around 10%.