The integration of robotic systems in knee arthroplasty has accelerated, with early results indicating improved precision and outcomes. The ROSA^® Knee System facilitates the robotic-assisted positioning of cutting guides while enabling real-time assessment of ligament balance, with the surgeon retaining control of all bone resections. This study aimed to evaluate the precision of implant positioning, achievement of the planned hip–knee–ankle (HKA) axis, and consistency across different operating surgeons. A prospective observational study was conducted on patients undergoing robotic-assisted total knee arthroplasty (RATKA) using the ROSA Knee System. Radiographic assessments included pre- and post-operative AP/lateral knee and long-limb radiographs, supplemented with post-operative CT to assess femoral component rotation. Intra-operative alignment data recorded by the ROSA console were compared to post-operative imaging. Complication rates were also evaluated. Among 94 knees analyzed, the mean difference between intra-operative and post-operative HKA measurements was 1.66 ± 2.09°, which was statistically significant. Minor but significant differences were observed in LDFA (0.32 ± 1.84°, p = 0.034), MPTA (0.84 ± 1.17°, p < 0.001), and femoral component rotation (1.63 ± 2.40°, p < 0.001). No significant variation was noted in LDFA or MPTA between surgeons, though differences were present in rotational alignment and HKA. The intra-operative HKA showed moderate correlation with both measured post-op HKA and arithmetic HKA (aHKA), with slightly stronger correlation with the latter. The ROSA Knee System enables reproducible and accurate implant positioning with reliable restoration of the planned HKA axis. Once a surgeon is proficient, results are consistent without increased complication risks.