Inquisition doesn't have "acts" like da2 though, right?
And you can talk to them at your leisure like in Origins (provided you are in relaxed areas like the keep), and in Origins if you had at least one option to start a romance left then right before the final battle you can start talking to someone and do the entire romance before starting the final saving of the city. Since you can go to the keep and talk to the companions whenever you might be able to do the same in inquisition.
No it doesn't look like it will have acts as such, but I wouldn't mind betting that there will be certain goals you have to achieve to win over your LI, like personal quests for example and they may be paced to run alongside the storyline.
Although we can theoretically go anywhere and do anything it would be quickly fatal to the party to jump into some areas until we are very high level and these may be some of the places we need to go to complete the romance goals.
For example
Cass will tell you she loves you on a moonlit tower overlooking Redcliffe village after you have recovered her father's shield from the dungeons and have romanced her for at least six meaningful interactions. Or she'll tell you she loves you after six meaningful interactions but can't rest at the thought of her fathers shield in Redcliffe dungeon.
Really unlikely example I'll admit, but you get the idea.
If unlocking the romance is tied to personal quests like DAO and to a lesser extent DA2 it may take some time in game just to be able to go to the places we need to finish those quests.
Here's a thought though will we be able to complete unfinished romances post game?