Preheat oven to 450 F / 230 C. Toss all ingredients in a bowl, spread onto a parchment lined baking sheet. Bake for 10-15 minutes. Cool until ready to use. Reserve strawberry syrup to brush on cake.
Preheat oven to 350 F / 175 C. Grease a 9" x 5" loaf pan, dust inside with flour, tap out extra.
Whisk together flour, baking powder, and salt in a bowl. In a separate bowl, whisk together sour cream and lemon juice.
In a mixer bowl with a paddle attachment on medium, beat butter, marzipan, lemon zest, and sugar until light, about 3 minutes. Add eggs in three additions, scraping the bowl and mixing until smooth - the mixture will start to curdle.
Add one-third of the flour mixture, then half of the sour cream mixture, mix on low speed incorporate. Repeat the step, scraping the bowl if necessary.
Using a silicone spatula, fold in roasted strawberries just until they are evenly distributed. Pour into prepared pan, leveling off with the spatula.
Bake cake in preheat oven for 55 minutes to 1 hour 10 minutes, until a cake tester comes out with a few crumbs. Cool for about 10 minutes before transferring to a rack.
Brush the reserved syrup onto the top and sides of the cake. Cool completely before serving, about 2 hours. Garnish with fresh strawberry slices and edible flowers, if desired. To store, wrap tightly in plastic in room temperature for up to 2 days.