Heat oven to 400ºF. Line a half sheet pan with foil and set aside.
Place the bell pepper, onion, garlic, zucchini, and olive oil in a medium mixing bowl and toss until the vegetables are coated. Spread the vegetables evenly on the prepared half sheet pan and roast, tossing occasionally, until the vegetables are soft and are beginning to turn brown around the edges, about 45 minutes. Remove from the oven and cool completely.
Transfer the vegetables to a food processor along with the cream cheese and process until well combined and spreadable; do not process until completely smooth.
Taste and season with salt and pepper, if desired. Spread on soft bread, such as challah, foccacia, or pita bread. Store in the refrigerator in an airtight container for up to 1 week.