1. In the food processor, pulse the graham crackers until fine crumbs. Alternatively, you can place the graham crackers in the ziplock bag and crush them with rolling pin until fine crumbs. Reserve 1/3 cup of crumbs.
2. In the double boiler over simmering water, combine semi-sweet chocolate and heavy cream and stir until the chocolate is melted and the mixture is smooth.
3. Line a baking sheet with a foil and spray cooking spray all over. Spread the mini marshmallows on the sheet and broil for 2-3 minutes, or until they are slightly browned and puffed a bit. Keep a close eye on them, it will take just seconds from perfect to burnt. Transfer the roasted marshmallows into the bowl with melted chocolate mixture. Stir in the graham cracker crumbs. Mix until well combined. Cover the mixture with a plastic wrap and let it cool and set for about 30-60 minutes. You may put in the fridge to expedite the process. Once the mixture is set, form the mixture into 1.5-inch truffles using a cookie scoop.
4. Place the reserved 1/3 cup of graham cracker crumbs in a ziplock bag and roll each truffle in the crumb. Arrange the truffles on a platter.
5. If desired, melt the white chocolate in the microwave according to the instructions on the packaging. Put the melted chocolate in a ziplock bag with a small hole cut out in one corner. Drizzle over the truffles to decorate. Keep refrigerated until ready to serve.