Self-massage tools such as foam rollers and massage balls are widely used in warm-ups and recovery, but their effects on dynamic strength tasks like squatting remain unclear. To compare the effects of a foam roller (FR), massage ball (MB), and vibrating massage ball (MBV) versus a control condition on squat load velocity profiles and associated electromyographic (EMG) activity in resistance-trained individuals. In this crossover study, fourteen experienced resistance-trained participants performed four experimental conditions: FR, MB, MBV, and control. After an initial session for incremental load testing and protocol familiarization, each participant performed eight back squats before and after each experimental session, while movement velocity, hip vertical displacement (range of motion), and EMG of the vastus lateralis and semimembranosus were recorded. MBV produced a significant increase in quadriceps EMG during the fastest repetition (β = 0.107; p = 0.003). In contrast, all interventions elicited a reduction in the second fastest repetition versus control (FR: β = -0.033, p = 0.005; MB: β = -0.025, p = 0.029; MBV: β = -0.036, p = 0.002). Moreover, both FR and MBV similarly decreased third fastest repetition and mean velocities relative to control (FR: third fastest repetition β = -0.025, p = 0.027; mean β = -0.046, p = 0.046; MBV: third fastest repetition β = -0.032, p = 0.005; mean velocity β = -0.031, p = 0.004). There were no significant changes in the hip vertical displacement. All self-massage conditions modestly impaired squat velocity, with the MB showing the least detrimental effect on performance.