 Role-playing games Siembieda has created include "Palladium Fantasy Role-Playing Game" (1983), "Heroes Unlimited" (1984), "Robotech" (1986), and "Rifts" (1990).He is also an artist, known for occasionally illustrating Palladium Books products.Siembieda contributed art and cartography to several early Judges Guild products for the "Dungeons & Dragons", "RuneQuest" and "Traveller" lines.