What does the Rome Statute have to do with the ongoing war in Ukraine? Neither Russia nor Ukraine ratified it, but the proceedings have commenced
The court has jurisdiction over crimes only if they are committed in the territory of a state party or if they are committed by a national of a state party; an exception to this rule is that the ICC may also have jurisdiction over crimes if its jurisdiction is authorized by the United Nations Security Council.
Perhaps it is a political move to force Russia to veto a resolution authorizing jurisdiction in the hope that most of the world would view as being tantamount to an admission of the impropriety of its invasion of Ukraine.
In addition, Ukraine has granted the court "ad hoc jurisdiction." See Ukraine fights Russia on the ground and in the courts:
The court is limited to investigating the crime of aggression to members of the court. Russia is not a party to the Rome Statute, which created the court in 2002, while Ukraine has granted the court only ad hoc jurisdiction since 2014. On that basis, the court completed an initial investigation into Russia’s activities in Eastern Ukraine and its 2014 annexation of the Crimean peninsula, concluding six years later that there was “a reasonable basis at this time to believe that a broad range of conduct constituting war crimes and crimes against humanity.”