Ok, I try.
The plot to kill Ceasar is thwarted.
He epurates the opposition and goes on to his planned campaign in Dacia. Ensuing mop-up leads to provincialization of Cimmerian Bosphorus and parts of modern Georgia, alongside the Carpathian and Wallachian plains (most of them). Caesar goes on to win some victories over Parthia securing Armenia and parts of northern Mesopotamia but he does not accomplish much more (i.e., Parthia is severely weakened but not crushed). However, Rome is uncontested hegemon in Asia Minor, Caucasus, the Balkans and places around. The Black Sea is a fully Roman lake as much as the Med.
After Caesar's death around 33 BCE, a messy political situation emerges that devolves into civil war. It's still more or less Octavian versus Ptolemy/Cleopatra, like IOTL, but the details and alignments obviously differ greatly. However, the endgame is roughly similar to OTL, Octavian comes out on top and annexes Egypt and some other Oriental states in the Roman sphere.
He lives about as long as IOTL, pursues roughly similar policies although he's somewhat bolder in expansionist strategies and luckier both in them and in his family life, securing a very competent successor (butterflies at this point would create someone unrecognizable). By 15 AD, the Elbe/Carpathians/Southern Bug line is more or less the Roman frontier. However, lacking a Teutoburg-like shock, the Romans keep pressing on. Emperors find prestigious to seal their legitimacy with relatively easy victories over Germanic tribes. It takes a couple centuries to stably push the border to about where the Eastern Polish border is now. Meanwhile, the North European plain is slowly developed and urbanized. The process is long and somwhat intermittent, but an earlier spread of a version of heavy plough allows it to go one. Gothic attacks through the Baltic force the Romans to pour more military attention to the areas, with infrastucture following, and then to counterattack themselves raiding southern Scandinavia.
The Balto-Slavic groups are painstakingly integrated into the Roman economic sphere although Rome does not bother to conquer them for the most part.
The British Isles are conquered in their entirety. The major military concern for the Romans in Europe are the steppe peoples of Sarmatia, although some of them begin a take a more sedentary and amicable lifestyle due to long-term direct contact with the Empire along a huge front. Parthia/Persia is also a problem, but Rome has a huge logistical and manpower advantage and also can access troops matching historical military advantages the Persians has (cavalry, mounted archers).
Imperial overstretch causes issues in the third century but sheer luck allows Rome to come across more or less intact and someone capable enacts needed reforms.
Development in Eastern Europe due to more proximity with Rome causes the area to become richer, more populated and somewhat urbanized, making some of those previously worthless areas a tempting target to Rome, who either conquers or vassalizes/integrates the area. Bloody campaigns sometimes bordering on genocide punctuate this exampansion, especially against rebellious steppe nomads.
At this point, all Rome needs to reach the Urals is some centuries and a massive streak of luck.