Rinse the red peppers and pat dry. Cut off the stems and remove seeds. Place the peppers on a baking sheet and roast in a preheated oven at 400°F (200°C) for about 25-30 minutes until the skins are charred and blistered. Remove from oven and transfer peppers to a bowl, cover with plastic wrap, and let them steam for 15 minutes to loosen the skins. Carefully peel off the charred skins and discard. Place the peeled peppers in a food processor and blend until smooth. Spread the pepper puree in a thin layer on a baking sheet lined with parchment paper. Dry the peppers in a dehydrator at 135°F (57°C) for 8-10 hours, or in an oven set to its lowest temperature with the door slightly open, until completely dry and brittle. Break the dried peppers into pieces and grind into a fine powder using a spice grinder or mortar and pestle. Mix in salt and smoked paprika if desired. Store the homemade paprika in an airtight container away from light.