Master Sergeant Manes Replaces Sheriff Valenti
There is actually a Sheriff Valenti in Roswell, New Mexico (played by Rosa Arredondo), but it doesn't appear as though she'll have as large a role to play as Sheriff Jim Valenti, the dogged lawman played by William Sadler in the original series. Though he eventually came to be an ally for the Pod Squad, Jim Valenti started out as Roswell's main antagonist and was an intimidating presence, seemingly always one step away from uncovering proof of the aliens' existence.
In Roswell, New Mexico, the authority figure trying to hunt down the aliens is Alex's father, Master Sergeant Manes. Again, this is a detail taken from the original novels, where Alex's father (usually referred to simply as "The Major") is in charge of the secret alien monitoring organization Project Clean Slate. It's indicated that Kyle's father was still involved in the hunt for aliens in Roswell, since on his deathbed he told Alex to "go to Manes" if he ever saw "the handprint." Through this instruction, Kyle ends up getting roped into Manes' hunt when he approaches him to discuss the glowing handprint on Liz's chest.
Michael's Relationship With Alex
One of the big reveals in Roswell, New Mexico's pilot was that of Michael's romantic relationship with Alex Manes. In the original series, Michael was straight and had a tumultuous but fan-favorite romance with Liz's best friend, Maria, so some Michael/Maria shippers were dismayed to see the show's reboot going in a different direction. However, showrunner Carina Adly McKenzie has confirmed in an interview with THR that Michael is bisexual and that the show "will be exploring Michael's relationships with women" as well, so don't rule out the possibility of Michael and Maria getting together down the line. In the meantime, Michael's relationship with Alex is a risky one, given that Alex's father is trying to hunt down the aliens in Roswell.
Alex Manes shares a first name with Alex Whitman, Liz's friend from the original series, who was played by Colin Hanks. However, the similarities appear to begin and end there. Alex Whitman was wise-cracking and nerdy, and definitely not a stoic soldier, and he had a romantic relationship with Isabel, not Michael. Alex Manes is a lot closer to his character in the novel (also called Alex Manes, not Whitman), whose father was "obsessed with his future military career," and it seems as though this version of Alex gave in to his father's wishes... at the cost of his leg. At the moment, Alex Manes' alliances are unclear: will his feelings for Michael overcome his desire to please his father, or could he prove to be a secondary antagonist?
Already in the pilot it's clear that Roswell, New Mexico will diverge from the story of Roswell, though it remains to be seen how much, and whether other classic characters like Tess will show up. Let us know in the comments what you thought of Roswell, New Mexico's pilot, and whether you're planning to keep watching.