Moon Lovers: Scarlet Heart Ryeo (2016)

Both has Time Travel.. On both one of the couple is from an old era, On Rooftop Prince he is from Joseon Era, On Scarlet Heart modern girl travels back to Goryeo Era. Both has got great love story

Similarities:
-Princes falling in love with a maid
-Rebellion
-inter competition between all the princes
-lover triangle
-The characters Wang Wook (Moon Lovers) and Yan Xun (Princess Agents) have a very similar goal, but end up hurting the one they love

Princess Agent has defiantly more danger and action pact.
-secret organizations

Moon Lovers: Scarlet Heart Ryeo focuses more on the romance and relationships between the Female main lead and the Princes.

Both are based on Chinese novels
Both are painful but you cannot help yourself but be enthralled by the plot, OST, acting, cinematography and the tragic love of the main leads.
They both have supernatural elements(one less than the other but still)
The supporting characters stories are really interesting and add to the main story

Though both sageuks have different target audiences in mind (they have differences as if you want some smart political talk you should watch Queen Seon Deok rather than Moon Lovers) they have sone similarities:
> lots of male fanservice (hwarangs in Queen Seon Deok, princes in Moon Lovers)
> the female leads love one man first then she turns to love a man with a darker past (plus both men wear black most of the time, I'm talking about Bidam and Wang So, Kim Nam Gil and Lee Joon Gi Yeah!)
>both the second men the female leads love have mothers that are obsesses with power plus those mothers abandoned those sons too
> both evil mothers have other sons they prefer over the son (the men loved by the female leads) they abandoned without realizing that their abandones sons are the smartest and their closest ticket to power

859 AD. The once-great Tang Dynasty is now declining. Numerous rebel groups have formed, the largest of which is the House of Flying Daggers, based in Feng Tian county. They steal from the rich and give to the poor, gaining the support of people. The local deputies have managed to kill their former leader, but the rebel group only becomes stronger, due to a mysterious new one. Jin and Liu, two police captains, are ordered to kill the new leader within ten days.

A tale of love and adventure between an immortal fox and an artisan goddess. An eternal love that will face enemies in heaven and on earth.

Tired of the men in her life being lying, married philanderers, Koharu moves away from the city and back home. Once there, she finds her family saddled with debt and no way out. That is until a handsome stranger offers to settle the debt if Koharu agrees to marry him. And if that wasn't crazy enough, he already has two wives!

Same plot...girl time travels to past. An amazing drama with amazing cast

Enredo trágico repleto de armações contra o casal principal, mentiras. Antagonistas cruéis. Cenas engraçadas, uma pitada de comédia.

Ok, these are clearly nothing alike. But after watching SHR, I wanted something with a questionably crazy male lead. Yoo Jung reminded me of Wang So because neither are the typical "jerks," but they are not really nice guys either and they both make me wonder if either is really sane lol. And they kind of treat the girl the same way.
And both have the same combination of romance with a bit of suspence and an open ending.

Both have the time travel genre, although there are some differences. In Moon Lovers, the girl travels back in time and in Queen In Hyun's Man, the guy is from the past and has the ability to travel to the future.
Both have historical elements (Moon Lovers has a lot more).
The romance is very satisfying in both of them. No tragedy in this one. Maybe some tears...^^

? Both Jin Mi and Hae Soo, the female protagonists, underwent a drastic character development from a silly girl to a matured woman. They serve the same vibe. Trust me and watch till the end for they are not same as they were in the first episode.
? There are parts where Xu Feng reminded me of Wang So especially when they look hot and brooding in all black ensemble. Xu Feng also became an emperor at one point. Unfortunately, unlike him Wang So failed to get the girl. (ANNYEONG PDNIMS, WE STILL NEED THAT MOON LOVERS SEASON 2 THOUGH.)
? Both OTPs showed a love that consumes you. You can't help but swoon and root for them. But, Jin Mi and Xu Feng's pairing triumphed above their circumstances which gave as a happy ending.
? Both Run Yu and Wang Wook, the brothers of the male protagonists, vied for the female leads' hearts. Their ambition for the throne also got in their heads making them the antagonists.

When a total eclipse of the sun takes place, Go Ha Jin is transported back in time to the start of the Goryeo Dynasty of Korea during King Taejo's rule. She wakes up in the body of 16-year-old Hae Soo and finds herself in the house of 8th Prince Wang Wook, who is married to her cousin. She soon befriends several of the princes and meets the ostracized 4th Prince, Wang So. Although she knows she should not get involved in palace intrigues over the succession to the throne, she inadvertently becomes a pawn in the struggle, as several of the Princes fall in love with her.
(Source: MyDramaList)

Both are time travel. The historical part around the same era. Several cute young men and one girl.

Both are romance historical dramas and sorta have the same method of time travel.