Ursa can kill Roshan when he reach level 5 if you are playing with your friend with 1v1. Ursa is capable of being carry, tanker, or just support. I suggest to learn her first skill only +1 when you reach level 5 or 7 to slow your enemies. Every level, learn only her 3rd skill or 2nd skill because first skill is only for hero. [This guide is for RS only

Here follow this step:
1. Buy Vladimirs [I suggest vladimirs because its not an Orb Effect]
2. Buy Boots [like: Threads, Phase boots]
3. Vanguard [Optional]
4. Reach level 5 or 6
5. Go to Roshan and kill him (Use 2nd skill to make your attack speed fast) [Make sure your friend is not MH or beside you]
6. If your friend discover that you are attacking roshan, slow him then kill him.
Remember: This guide is only Basic.