Tone, if you look at this map,I'll try to approximate the provinces here with the ones in RS 2 to allow for province groupings.
I used the RS Map from the Printable RS2 Map thread as a reference.
Linky:
Starting with Britannia:
RS2 Provinces: Terrae_Ordovices, Terrae_Brigantes, Terrae_Trinovantes, Terrae_Dumnoii (and assuming the player has them, Hibernia & Caledonia)
Germania Inferior:
RS2 Provinces: Terrae_Atrebates, Terrae_Nervii,
Germania Superior:
RS2 Provinces: Sequania, Terrae_Volcae, Helvetii,
Rhaetia (not strictly part of Germania Superior, but it does make grouping easier).
The Three Gauls: (Belgica, Lugdunensis and Aquitania)
RS2 Provinces: Terrae_Bellovacorum, Terrae_Suessiones, Aulercia, Armorica, Lemovicia, Aeduia, Aquitania, Arvernia
Gallia Narbonensis:
RS2 Provices: Narbonensis, Transalpine_Gaul, Lugdinensis.
Hispania Tarraconensis (looking at the map of the Roman Empire, this one covers a HUGE chunk of the Iberian peninsula):
RS2 Provinces: Gallaecia, Asturia, Cantabria, Celtiberia, Ceretania, Beribracia, Bastetania, and Baliares.
Baetica:
RS2 Provinces: Carpetania, Turdetania
Lusitania:
RS2 Provinces: Lusitania, Vettones, Tartesania
Gallia Cisalpania:
RS2 Provinces: Taurini, Cisalpine_Gaul, Venetia, Liguria, Aemillia.
Sardinia et Corsica:
RS2 Provinces: Sardinia, Corsica (surprise surprise)
Sicilia:
RS2 Provinces: Sicilia_Poenicum, Sicilia_Medius, Sicilia_Romanum, Sicilia_Graecus (again another big surprise)
Africa Proconsularis:
RS2 Provinces: Zeugitania, Byzacium, Byzacium_Africanus, Tripolitania
Numidia & Mauretania (combined for convenience):
RS2 Provinces: Numidia, Terrae_Massyli, Mauretania_Massaesili, Mauretania_Tingitania
Pannonia Superior and Inferior (again, combined because it's easier - and the Pannonian legions all chose to back Vespasian in the Civil war, so combining them isn't exactly bad):
RS2 Provinces: Pannonia_Superior, Pannonia_Inferior, Gaia_Skordiskon
Noricum, again, not strictly part of them, but if you want large clumps this isn't too far-fetched,
Dalmatia:
RS2 Provinces: Illyria, Dalmatia, Illyricum.
Moesia Superior & Inferior (Combined because it makes sense to do so)
RS2 Provinces: Moesia, Paionia, Ano_Thraike, Hellenike_Skythia, Olbike_Skythia.
Dacia:
RS2 Provinces: Dacia_Minor, Dacia, Getia, Mikre_Skythia
Thrace:
RS2 Provinces: Thraike, Parastrymonis, Thraikike_Chersonesos, Propontis, Gaia_Thynon
Macedonia and Epirus (combined because Epirus is tiny):
RS2 Provinces: Makedonia, Ano_Makedonia, Khalkidike, Epeiros, Thessalia, Aitolia.
Achaia
RS2 Provinces: Boiotia, Euboia, Attike, Achaia, Argolis, Elis, Lakonia.
Asia:
RS2 Provinces: Troas, Mysia, Ionia, Caria, Rhodos, Lydia, Phrygia
Lycia et Pamphilia:
Lykia, Pamphylia (surprise surprise)
Galatia:
RS2 Provinces:
Galatia and Pisidia
Pontus et Bythynia:
RS2 Provinces: Bithynia, Paphlagonia_Graecus, Paphlagonia, Pontos
Cappadocia:
RS2 Provinces: Kappadokia, Pontos_Paraktios, Mikre_Armenia, Kommagene, Sophene
Syria, Judea & Cilicia (Cilicia is tiny, and Judea was technically under the overall control of the governor of Syria anyway):
RS2 Provinces: Kilikia, Kypros, Kyrhessike, Seleukis, Koile_Syria, Phoenike, Ioudaia, Gaza.
Aegyptus & Arabia (combined to make things easier.):
RS 2 Provinces: Petraia_Arabia, Sina, Delta_Anatolikon, Delta_tou_Neilou, Marmarike, Heptanomis, Thebais, Dodekaschoinos.
Cyrenaica et Creta: Krete, Kyrenaike_Esperia, Anatolike_Kyrenaike.
I'm not sure about the two provinces above, marked in red - Rhaetia and Noricum. If you like, these two can be wholly independent of Germania Superior and the Pannonias respectively, and rebel idividually, or be grouped into an Alpine Provinces type of thing so they rebel together.
Italy (i.e. south of Liguria and Aemilia - so the player's northern border at the beginning of the campaign) hasn't been combined, so you can have as much patchiness there as you like, as it is the Roman heartland in a Roman civil war.