diff --git a/src/mame/machine/namcoio.cpp b/src/mame/machine/namcoio.cpp
index 3503b47a981..f3e39cbdc8a 100644
--- a/src/mame/machine/namcoio.cpp
+++ b/src/mame/machine/namcoio.cpp
@@ -519,3 +519,34 @@ READ_LINE_MEMBER( namcoio_device::read_reset_line )
 {
 	return m_reset;
 }
+
+
+ROM_START(namco_56xx)
+	ROM_REGION(0x400, "mcu", 0)
+	ROM_LOAD("56xx.bin", 0x0000, 0x0400, NO_DUMP)
+ROM_END
+
+ROM_START(namco_58xx)
+	ROM_REGION(0x400, "mcu", 0)
+	ROM_LOAD("58xx.bin", 0x0000, 0x0400, NO_DUMP)
+ROM_END
+
+ROM_START(namco_59xx)
+	ROM_REGION(0x400, "mcu", 0)
+	ROM_LOAD("59xx.bin", 0x0000, 0x0400, NO_DUMP)
+ROM_END
+
+const tiny_rom_entry *namco56xx_device::device_rom_region() const
+{
+	return ROM_NAME(namco_56xx);
+}
+
+const tiny_rom_entry *namco58xx_device::device_rom_region() const
+{
+	return ROM_NAME(namco_58xx);
+}
+
+const tiny_rom_entry *namco59xx_device::device_rom_region() const
+{
+	return ROM_NAME(namco_59xx);
+}
diff --git a/src/mame/machine/namcoio.h b/src/mame/machine/namcoio.h
index 7f92e741043..1b7c23f25bf 100644
--- a/src/mame/machine/namcoio.h
+++ b/src/mame/machine/namcoio.h
@@ -60,6 +60,8 @@ class namco56xx_device : public namcoio_device
 public:
 	namco56xx_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 
+	virtual const tiny_rom_entry *device_rom_region() const override;
+
 	virtual void customio_run() override;
 };
 
@@ -68,6 +70,8 @@ class namco58xx_device : public namcoio_device
 public:
 	namco58xx_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 
+	virtual const tiny_rom_entry *device_rom_region() const override;
+
 	virtual void customio_run() override;
 };
 
@@ -76,6 +80,8 @@ class namco59xx_device : public namcoio_device
 public:
 	namco59xx_device(const machine_config &mconfig, const char *tag, device_t *owner, uint32_t clock);
 
+	virtual const tiny_rom_entry *device_rom_region() const override;
+
 	virtual void customio_run() override;
 };