Preheat oven to 400°F. Spray Coil Cakes Mini Cake Pan with vegetable pan spray and dust with cocoa powder.
In large bowl, sift together cocoa powder and flour. Add sugar to mixture and sift again; set aside.
In large bowl, whip egg yolks with electric mixer on high speed until light and fluffy, about 5 minutes.
In clean bowl with clean whip, whip egg whites and salt until foamy. Add cream of tartar and continue to beat until stiff but not dry. Fold 1/3 of egg whites into yolks until just blended; add remaining egg whites and flour mixture. Add vanilla extract. Gently fold together until no streaks remain. Divide batter evenly into cavities, spreading to edges. Cavities should be about 1/2 full.
Bake 7-9 minutes or until toothpick inserted in center comes out clean. Remove from oven. One at a time, loosen edges of cakes with butter knife and immediately turn out onto clean paper towels or parchment paper; trim away crisp edges of cake. While still hot, roll cake up in paper towel or parchment paper from short side. Repeat with remaining cakes. Cool completely.
In large bowl, beat butter and sugar with electric mixer until well combined, scraping down bottom and sides of bowl as necessary. Add vanilla and milk and beat until light and fluffy. Unroll cooled cakes and spread with filling. Reroll tightly. Position cakes on cooling grid set on a cookie sheet to glaze.
Melt candy according to package directions. Stir in oil until well combined. Pour glaze over tops of cake rolls. Tap cookie sheet on countertop to even glaze. If needed, glaze can be scraped from cookie sheet, gently reheated, and repoured over cakes. Refrigerate for 10 minutes. Gently slide a spatula underneath each cake roll to release from cooling grid.