dota-2 – What Does the Number Below the Clan-Logo Mean in Dota 2?

It's an indicator whether or not their ultimate is up.

If the gem is blue, it indicates that the ultimate is off cooldown, but they don't currently have the mana to cast it (credit to @Decency)

League of Legends has something similar.

With good control, any 5 heroes can kill Roshan before the match begins. It takes a good amount of teamwork and some money spent on health potions, however, and is easily punished if the opposing team realizes it. Because of this, the strategy is rarely seen.

There are certain heroes who are more effective at killing Roshan because of how their abilities work at level 1, and the increased speed or less punishment taken makes level 1 Roshan kills more common when some or multiple of the following are on a team:

• Ursa (Fury Swipes stacks indefinitely)
• Auras (Skeleton King, Luna, Drow, Beastmaster, Shadowfiend)
• Lich (Frost Armor slows Roshan attack)
• Venomancer (Wards can deal damage)
• Vengeful Spirit (Howl reduces armor by 2)
• Viper (Corrosive skin damages and slows attack speed)
• Any summoner plus Enigma. (Beastmaster, Nature's Prophet, Lycan, etc.). You can convert that summon into Eidolons and use further summons to damage, depending on hero.
• Lone Druid
• Wisp (Double effectiveness of Healing Salves with Tether)
• Timbersaw (Reactive Armor)

The reward is significant. Heroes will be halfway to level 3 if all split the experience, or if coordinated well one hero can be the only one within experience range and jump all the way to level 5. Each hero receives 200 gold and the killer gets a gold bounty of between 105-600 bonus gold. And, of course, the Aegis of the Immortal drops.

Items that help:

• Ring of Basilius for the +2 armor aura is an obvious one.
• Healing Salves. You can take turns tanking Roshan and healing quickly thereafter.
• Smoke of Deceit. If you're coming from the Radiant side, you're likely to be spotted without this. It also wears off when the enemy is nearby so you can know if you've been spotted on the way in. It also increases movement speed to get you there faster.
• Stats and regen. You are going to lane after this, and the bonus health and damage helps here too.

It's worth noting that the most popular combo recently is simply Ursa plus Skeleton King. Two coordinated players can kill Roshan by themselves with these heroes. Here's a video walkthrough I made to doing this: