This is the 8493rd most frequent Chinese word.
russo
The Chinese word "俄语 (俄羅語)" translates to "Russian language" in English.
In this sentence, '俄罗斯' (Russia) is used as a noun referring to the country. It describes the nationality of the friend.
我有一个俄罗斯朋友，他的名字叫亚历山大。
I have a Russian friend whose name is Alexander.
Here, '俄语' (Russian language) is derived from '俄罗斯' and specifies the language spoken in Russia.
学习俄语有一点困难，但非常有趣。
Learning Russian is a bit difficult but very interesting.
Here, '俄罗斯' is used adjectivally as a noun adjunct to specify the type or origin of the culture being referenced.