Objectives: This study aimed to explore the effects of four days of Rhodiola Rosea (RR) supplementation on bench-press and bench-pull exercises under resting or mental fatigue conditions in young healthy individuals. Methods: Eighteen participants (seven women) visited the laboratory on five occasions separated by 7 days—one preliminary session and four experimental sessions. In the preliminary session, participants were familiarised with the Stroop and Multiple Object Tracking tests, after which their one-repetition maximum loads for bench presses and bench pulls were determined. The four experimental sessions had the same protocol, differing only in the supplement (RR or placebo) and mental task conditions (Stroop test or control video). Participants were assigned randomly and counterbalanced to each experimental condition: (I) RR and Stroop test, (II) RR and control video, (III) placebo and Stroop test, and (IV) placebo and control video. Results: The main findings indicate that RR supplementation has trivial-to-small effects in terms of mental fatigue, visuo-cognitive processing, or perceived exertion. However, RR was significantly superior to placebo on strength performance in the control video condition during some sets, as it increased the number of repetitions performed in the bench press and the fastest velocity in the bench pull. Out of 52 comparisons, 17 small effect sizes were observed, with 14 favouring RR and 3 favouring placebo, with the remaining differences being trivial. Conclusions: These results suggest that short-term RR supplementation is safe and provides its main ergogenic effects on physical performance rather than in visuo-cognitive or mental outcomes.