Recently I try to find a new game that I can play with two of my friends. Usually we would like to play in one team and co-op against AI.
My question is, if only I have DLC, can I create a room, and make my friends also enjoy my DLC?
Thanks foe your attention and kindness.

FAQ from Jey in other forum:
"How do DLC work?
In solo games, you need the DLC or its content is entirely unavailable (can't play with it, can't play against it).

In multiplayer games:
If you want to play as a faction, you need to have the faction DLC.
If you want to use units from unit DLC, the host needs to have the unit DLC and activate it in the lobby settings.

Are there any recommended DLC?
DLC only contains what they say. They don't provide additional mechanics or features."

From Hay in other forum:

"There are 2 Types of DLC:
- Faction DLC
- Unit DLC

============= FACTION DLC ==============
- Only player that owns a faction DLC will be able to PLAY AS and also PLAY AGAINST the DLC faction

- Example - I own the base (SM, AsM, O, N) game and Tau expansion (T), I get to play as the 5 race I bought and not the other 4 I did not buy (AdM, Ty, CA, CSM) for both online and offline.

In Offline games, I can ONLY play against AI of the 5 factions I own, NOT the 4 that I do not own.

in Online games , I can play as the 5 race I bought, and other players can play with the faction they bought.

If 1 have Base + Tau = SM AsM, O, N, T
If others have Base + Chaos + Tyranids = SM, AsM, O, N, CSM, Ty

NOTE that choices of AI players faction depend on the host, so even if I as a joiner have CSM and TY, but host only has Tau, then Host cannot select AI as CSM or Ty. Host can only select the base faction or Tau for the AI.

============== UNIT DLC ================
Unit DLC provides additional units to the faction that you own.

As long as the host of the game (offline or online) owns the unit DLC (escalation pack for example), then host can enable it as part of game set up.

This will allow the AI to also make use of the additional Units.

In the case of an online game, if Host has all Unit DLC then joiners would also be able to take advantage of those additional units.

==== NEUTRAL BUILDINGS/ENEMIES/ITEMS ====
Regardless of having the DLC or not, the neutral items like enemies, buildings, equipment applies to base game.

You don't need Tau expansion to see Vespid Stingwing and Kroot hounds..

LORD OF SKULLS is a special case but again, if Host has it, host can enable it to add a natural boss that pawns in and ruin everyone's (including AI) day at random."