The development of sustainable, high-performance asphalt modifiers is a critical research area. In that sense, this study investigates the rheological properties of lignin nanocarbon (LNC), a pyrolysis-derived biomaterial, as a modifier for 50/70 penetration-grade asphalt binder. LNC was blended at 0.01% and 0.5% by weight, and its performance was benchmarked against the base binder and four commercial SBS-modified asphalts. A comprehensive analysis was conducted using Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests, following RTFO and PAV aging. Key parameters for rutting (MSCR Jnr3.2 and BTSV), fatigue (LAS-derived FFB, Δ|G*|peak τ, and GRP), and low-temperature cracking (ΔTc) were evaluated. Results indicated that LNC significantly enhanced rutting resistance, reducing Jnr3.2 from 3.48 (base) to 1.29 (0.5% LNC). It also increased intermediate temperature stiffness, exceeding the 5,000 MPa GRP limit, and improved fatigue indices. However, the LNC binders exhibited a primarily viscous response (δBTSV > 81º), lacking the superior elastic recovery characteristic of the SBS binders (δBTSV < 74º), which achieved Jnr3.2 values as low as 0.045. LNC acted as an effective stiffening agent, while SBS provided superior overall rheological performance.