Question: Tiberious and Germanicus were part of what empire?

Context paragraphs:
Germanicus: Germanicus (24 May 15 BC – 10 October AD 19), formally Germanicus Julius Caesar, was heir-designate of the Roman Empire under Tiberius and a prominent general known for his campaigns in Germania.

Upper Germanic-Rhaetian Limes: The Upper Germanic-Rhaetian Limes (German: "Obergermanisch-Raetische Limes" ), or ORL, is a 550-kilometre-long section of the former external frontier of the Roman Empire between the rivers Rhine and Danube.  It runs from Rheinbrohl to Eining on the Danube.  The Upper Germanic-Rhaetian Limes is an archaeological site and, since 2005, a UNESCO World Heritage Site.  Together with the Lower Germanic Limes it forms part of the "Limes Germanicus".

Nederrijn: Nederrijn ("Nether Rhine"; not to be confused with the section called Lower Rhine further upstream) is the name of the Dutch part of the Rhine from the confluence at the town of Angeren of the cut-off Rhine bend of Oude Rijn and the Pannerdens Kanaal (which was dug to form the new connection between the Waal and Nederrijn branches).  The city of Arnhem lies on the right (north) bank of the Nederrijn, just past the point where the IJssel branches off.  The Nederrijn flows on to the city of Wijk bij Duurstede, from where it continues as the Lek.  The once-important but now small Kromme Rijn branch (in Roman times part of the Limes Germanicus and border river of the Roman Empire) carries the name "Rhine" towards the city of Utrecht.

Raetia: Raetia ( or , ] , also spelled Rhaetia) was a province of the Roman Empire, named after the Rhaetian ("Raeti" or "Rhaeti") people.  It bordered on the west with the country of the Helvetii, on the east with Noricum, on the north with Vindelicia, on the west with Transalpine Gaul and on the south with Venetia et Histria.  It thus comprised the districts occupied in modern times by eastern and central Switzerland (containing the Upper Rhine and Lake Constance), southern Bavaria and the Upper Swabia, Vorarlberg, the greater part of Tirol, and part of Lombardy.  Later Vindelicia (today south-eastern Wuerttemberg and south-western Bavaria) formed part of Raetia.  The northern border of Raetia during the times of Augustus and Tiberius was the River Danube.  Later the Limes Germanicus marked the northern boundary, stretching for 166 km north of the Danube.  Raetia linked to Italy across the Alps over the Reschen Pass, by the Via Claudia Augusta.  The Romansh people living in Southeast Switzerland are believed to be direct descendants of the Raetians.  However, the exact lineage of the Romansh (or Romansch) people remains incomplete.

Tiberius: Tiberius (Latin: "Tiberius Caesar Dīvī Augustī Fīlius Augustus" ; 16 November 42 BC – 16 March 37 AD) was a Roman emperor from 14 AD to 37 AD.  Born Tiberius Claudius Nero, a Claudian, Tiberius was the son of Tiberius Claudius Nero and Livia Drusilla.  His mother divorced Nero and married Octavian, later known as Augustus, in 39 BC, making him a step-son of Octavian.

Navis lusoria: A navis lusoria (, plural "naves lusoriae" ) is a type of a small military vessel of the late Roman Empire that served as a troop transport.  It was powered by about thirty soldier-oarsmen and an auxiliary sail.  Nimble, graceful, and of shallow draft, such a vessel was used on northern rivers close to the "Limes Germanicus", the Germanic border, and thus saw service on the Rhine and the Danube.  The Roman historian Ammianus Marcellinus mentioned the "navis lusoria" in his writings, but not much about it could be learned until the discovery of such boats at Mainz, Germany in 1981–82.

Drusus Julius Caesar: Drusus Julius Caesar (7 October 13 BC – 14 September AD 23), was the son of Emperor Tiberius, and heir to the Roman Empire following the death of his adoptive brother Germanicus in AD 19.

Limes Germanicus: The Limes Germanicus (Latin for "Germanic frontier") was a line of frontier ("limes") fortifications that bounded the ancient Roman provinces of Germania Inferior, Germania Superior and Raetia, dividing the Roman Empire and the unsubdued Germanic tribes from the years 83 to about 260 AD.  At its height, the limes stretched from the North Sea outlet of the Rhine to near Regensburg (Castra Regina) on the Danube.  Those two major rivers afforded natural protection from mass incursions into imperial territory, with the exception of a gap stretching roughly from "Mogontiacum" (Mainz) on the Rhine to Castra Regina.

Ernst Fabricius: Ernst Christian Andreas Martin Fabricius (Darmstadt, 6 September 1857 – Freiburg im Breisgau, 22 March 1942) was a German historian, archaeologist and classical scholar.  Between 1882 and 1888 he participated in excavations in Greece and Asia Minor and also pioneered German research on the Roman Empire border defenses known as the Limes Germanicus.

Gaius Fonteius Capito (consul AD 12): Gaius Fonteius Capito (fl.  AD 12) was a politician of the early Roman Empire.  He served as consul alongside Germanicus in AD 12, and later as proconsul of Asia.

Supporting paragraphs: Germanicus Tiberius
Answer: Roman Empire