Roller-compacted concrete, due to its desirable mechanical strength, suitable compactability, high construction speed, and economic feasibility, is considered a suitable material for pavement construction. However, repeated freeze–thaw cycles can generate internal pressures caused by water freezing, promote microcrack development, and increase porosity, thereby leading to gradual deterioration of mechanical properties and durability. This study investigated the multiscale effect of partially replacing cement with alumina powder (Al₂O₃) on the mechanical behavior, abrasion resistance, and durability of roller-compacted concrete pavement under freeze–thaw cycles. Alumina powder was incorporated at 0, 5, 10, and 15% as a partial cement replacement, and specimens were subjected to 0, 50, 100, and 150 freeze–thaw cycles after 28 days of curing. Compressive strength, flexural strength, abrasion, and water absorption were evaluated at the macroscopic scale, while microstructural characteristics were examined at the microscopic scale. The results indicated that the mixture containing 10% Al₂O₃ exhibited the best overall performance. Compared with the control mixture, its compressive strength increased by 4.09, 9.98, 10.19, and 11.20% after 0, 50, 100, and 150 cycles, respectively. The corresponding increases in flexural strength were 8.13, 13.47, 14.81, and 14.30%. Moreover, abrasion decreased by 13.42, 14.45, 14.42, and 14.58%, while water absorption decreased by 6.32, 7.39, 7.32, and 7.58%, respectively. Microstructural observations revealed a relatively dense and continuous matrix in the 10% Al₂O₃ mixture, with a substantial portion of structural integrity preserved after freeze–thaw cycling. The simultaneous improvement in mechanical properties, abrasion resistance, and water absorption can be attributed to the filler effect of fine Al₂O₃ particles, enhanced matrix densification, reduced water penetration pathways, and limited freeze–thaw damage. Overall, 10% Al₂O₃ replacement was identified as the optimum content within the investigated range and demonstrated considerable potential for improving the performance and durability of roller-compacted concrete pavement under repeated freeze–thaw conditions.