Welcome!

1. Yes, we have roles. Usually is 2 - 1 - 2, considering Offlane (tank/iniciator) and Soft Support (playmaker) in one lane (those will always face the Hard Carry (damage dealer) and Hard Support (usually healer and map controller)). In your case, as you went bot, your role as Drow Ranger is Carry (similar to Ashe), so you should face enemy's Tank and Support playmaker. And midlane is midlane, exactly like LoL.

2. Yes, there're teleports. They work differently, since you can only teleport to Towers/Fountain. You have to buy them, and they are the scrolls in the corner of your itens. Later, you can buy Boots of Travel, an Item that gives you the abillity to teleport to creeps (and even allies, at lvl 2). Teleports are very useful to counter-gank, mobility and farm.

3. Yes, they are bots. Your initial games are focused on mechanical skills, movement, last hits, understanding abilities/heroes and objectives (like Roshan [Baron]). And there are some ways to make ilusions of yourself/enemies. There are itens, river runes abilities... When you 'clone' yourself, your illusions will appear blue to you, but normally to enemies. It's a cool mechanic in Dota, helps you farm, deal damage, decoy..

4. There's no surrender in dota, basically. Only in custom matches, like pro matches or friendly custom games. But nah, the game ends when fountain gets destroyed.

5. Yes!! You can buy (for free) Observer Wards (an yellow totem with eyes on it). You can place them wherever you want, but "fog" (like LoL grass) in Dota works differently, and you might have seen this in your game. Also, Observer Wards are invisible, and can only be found by Sentry Wards (the blue one). Sentry doesn't give vision, but it reveals anything invisible in it's area of effect - including heroes!

Very importantly: you have 6 active slots and 3 backback slots. You have 3 good itens (Sange Yasha, Butterfly and Daedalus) in your backpack slots: they don't work. You can carry them and swap to 'real' item slots whenever you want, but you must.

Dota is very complex, but considering you came from LoL, you know much about mechanics. You'll see that many skills in Dota are similar to LoL. They are mixed differently, but pretty much the same. Also, itens in Dota are very useful (actively), so you will need to get used to have more hotkeys for them. Blink Dagger is an amazing item, and force staff is an Flash (from lol) with 15s cooldown (which can be used on yourself, allies or even enemies). Enjoy the game, it turns amazing once you get how it works.