This undecorated Roman lamp is named after a nearly identical found in Roman London in the vicinity of the Thames. The original lamp this was molded from, as well as the one from the Thames, were both probably made in northern Italy and imported. This lamp would date to the mid or late 1st century AD through the 2nd century AD.
Molded directly from the original.
(about 2.75" x 3.75") 

This type of oil lamp is called a firmalampen, which essentially means "factory lamp." These lamps were made in large quantities in lamp workshops all over the Roman empire, but most especially in northern Italy. Many feature a maker's mark on the base. As an interesting sidelight, a firmalampen of this exact style found in Jerusalem has the inscription HEROD in Greek letters on its base. Modeled after the original in the link.
(3.5" x 2.5")

The crescent moon and star suggest this may have been a  lamp symbolizing the goddess Selenus or Luna. 
Molded directly from the original
(about 3.75" by 3") 

By popular request- Aquila, a lamp with a representation of an eagle for the Roman legionaries to light up their camps. The lamp body is cast from the same original lamp as the Luna.  (about 3.75" by 3")

The discus of this reproduction Roman lamp features Eros or Cupid, carrying a torch. This cupid is very similar to one on an original lamp excavated from Roman period ruins at Corinth, Greece.  The lamp body is cast from the same original lamp that produced the Luna above. 
(about 3.75" by 3")

The lion was not only popular as a figure on its own in Roman art, but also frequently appeared in conjunction with other Roman figures such as Hercules and Cybele. Lions are also often found in scenes with other animals, usually attacking. This replica Roman lamp has a body cast directly from the same original used to create the Luna. 
 (about 3.75" by 3")

Ostia was the primary port for the city of Rome, and many amphorae of wine passed through its gates over the centuries. Grapes were a symbol of plenty for peoples all over the Roman Empire and the ancient classical world. They were also closely tied to the Roman god Bacchus, who was patron of wine. The body of this replica Roman lamps is cast from the same original lamp used to make the Luna. (3.75" by 3")

A plain firmalampen, this style came into fashion about AD 70. An original Roman lamp mold was used to form the base of this lamp. It is utilitarian in nature, and has no decoration, but was a very common lamp style for about two centuries. The most prolific maker's mark on these lamps is "FORTIS", a north Italian maker which apparently sent out molds to branch lamp makers, but was also widely copied, maker's mark and all. This lamp carries my own marker's mark, FIGVLI (Literally, "of Figulus"). (about 2.5" x 3.75") 

The city of Volterra, in the present province of Pisa, is home to a well preserved Roman theater. This firmalampen features a theater mask molded directly from an original lamp (the Plautus, below). The mask is then placed on a lamp body formed from an impression taken from an original Roman lamp mold. A northern Italian lamp type.
(about 2.5" x 3.75")

This theater mask lamp dates from about AD 50 to sometime in the 2nd century. Plautus was a popular Roman playwrite, who penned such comedies as Miles Gloriosus and Pseudolus (both of which were adapted into the 1960's  A Funny Thing Happened on the Way to the Forum).
Molded directly from the original.
(about 4" x 3") 

Named for the Roman baths at Bath, England, this lamp features Aphrodite Accroupie (Venus at the Bath), and uses a body molded directly from the original above.  The image was well known in the ancient world, and sculpted in marble by such artists as Praxiteles.
(about 4" x 3")  

The body molded directly from an original, this lamp dates to about AD 50 to the 2nd century. A plain utilitarian style. Mutina is the ancient Roman name for Modena, a major lamp production center in north-central Italy.
(about 4" x 3")