This study aimed to determine the effect of substitution of wheat flour with purple sweet potato flour on the end-quality and antioxidant activity of the resulting roll cakes. Furthermore, the objective was to determine the optimal percentage of the substitution of wheat flour with purple sweet potato flour that would be graded as the best and most preferred by the panelists. This study used a completely randomized design (CRD) with 5 treatment levels and 3 replications. Observational data were analyzed using analysis of variance (ANOVA) and Duncan's New Multiple Range Test (DNMRT) at 1% significance level. The treatment in this study was the substitution of purple sweet potato flour for wheat flour in the manufacture of roll cakes, namely 20, 30, 40, 50 and 60%. The results showed that the substitution of purple sweet potato flour for wheat flour in the production of sponge rolls had a very significant effect on the content of water, ash, fat, protein, crude fiber, carbohydrates, and had no significant effect on antioxidant activity. The most preferred sponge cake was treatment E (substitution of purple sweet potato flour for 60% wheat flour) with a moisture content of 8.65%, ash content of 1.19%, fat content of 17.41%, protein content of 10.18%, crude fiber content 19.23%, carbohydrate content 62.56%, and antioxidant activity 62.47%.