The steamrolling tactic consists in en masse building of a few complementary armored types, and sending them rampaging straight away onto the enemy. Its sole advantage is its sheer brute firepower. It's also plain fun to smoke the enemy in an overwhelming mass of units. The downsides are, however, numerous and annoying. It is incredibly time and resource consuming, provides for completely inflexible formations, and makes easy prey for any area damage weapons. As a matter of fact, this tactic is only an option in a team game, and then only when you have already eliminated an opponent and taken over his resources.
All Factions
Tanks — This tactic makes you deploy up to 12 or more Tanks. Depending on the faction you are playing this Tank Steamrolling attack may work on various ways when steamrolling with the Tanks.
Allies
Multigunner IFVs - Build 13 Multigunner IFVs and load them with 5 Peacekeepers, 5 Javelins and 3 Engineers. Send them to enemy's base. Engineer IFVs repair your other IFVs, Peacekeeper IFVs handle infantry and Javelin IFVs handle most of vehicles and aircraft. This works as guerilla tactic, too. You may also send Engineer IFV nearby enemy Construction Yard, deploy IFV and capture enemy ConYard.
Mixed assault - A mix of Cryocopters, Apollos, Peacekeepers, Javelin Soldiers and at least 12 Guardian tanks will offer you decent results.
Amphibious assault - On sea, swap your Ground units for at least 5 Aircraft carriers and 12 Assault Destroyers. Mirage Tanks and Athena Cannons are another powerful option on steamrolling your enemies as well as Century Bombers.
Three Pronged Assault: Air, Land and Sea - For this technique, you should use the time bomb and strategic bomber protocols. A good option is to load up four century bombers with 10 peacekeepers and 10 Javelin soldiers. Build at least two aircraft carriers and at least six Assault Destroyers and two hydrofoils for defense of the carriers (the Destroyers can also be used to aid the para drop when defenses are dealt with). Pull your carriers and their screen to nearby the enemy base and allow their squadrons to auto attack defenses and structures. When they have cleared a path, send in a cryocopter to scout so you can use your protocols to further weaken the enemy. When you feel confident your bombers wont get shot down, have them attack the enemy construction yard and then paradrop your forces into the base, while simultaneously sending in your Assault Destroyers to provide support to the ground troops. You should quickly decimate the enemy base using this method. If your on a land locked map, use Athena Cannons instead of carriers and Guardian tanks instead of Assault Destroyers.
Soviets
The most suited faction for steamrolling, as their "mass production" protocol reduces production costs by 25%. Also to their advantage is their ability to build simultaneously multiple tier 2+ factories without the need of individual upgrades.
Mixed assault - Swarms of Twinblades, MiGs, Kirovs, Bullfrogs, tanks and Artillery units will serve you well.
Apocalypse Tanks - Building huge battalions of Apocalypse Tanks is another option for steamrolling but it will be expensive.
Hammer Tanks - A cheaper alternative to Apocalypses. Build 12–15 Hammers and go to the enemy's base. Rush over infantry and Leech Beam down enemy vehicles. You get their weapons to eliminate aircraft. Leech Beam also is quite good against structures – your Hammers get health and structures go down. The bad thing is if your enemy has swarms of anti-tank infantry/aircraft, your Hammers won't make it.
Empire of the Rising Sun
Naval battles are often won by few Shogun Battleships with Tsunami Tank and Sea/Sky-wing support.
Ground assault - Building 12 Tsunami Tanks, 12 Imperial Warriors and 12 Tankbusters backed up with Jet Tengu support will serve you well, along with King Onis and Wave-Force Artillery.
Air assault works with a mix of Chopper-VXs, Jet Tengus, Sky-Wings and Rocket Angels (with their special ability).
Tsunami Tanks - A huge battalion of Tsunami Tanks also works. When anti-tank infantry irritates, activate Nanodeflectors and crush them. Beware of enemy aircraft.