They're functionally equivalent. Both are lower level hydraulic brakes that work well. The BR-M315 Shimano is in the "Altus" groupset. Tektro's lowest "label", I think, is Auriga, and that's on M3xx series brakes I believe. Maybe M295. I'm not as familiar with Tektro's line. My Giant ARX had Tektro HD-M285 brakes and I can tell no functional difference between them and the Shimanos on my Roam. In fact, they use the identical brake pad application part number and pads are directly interchangeable between them.

The 2019 Roam 2 actually uses an Acera drivetrain. The front derailer will be an FD-T3000 and the rear derailer will be an RD-M3000. These are very functional and you'll enjoy good shifting performance. The shifters themselves are Altus level shifters, and I replaced the shifters with Acera ST-M3000 shifters and it actually seems to shift better with the Acera shifters. But still functional with Altus. I agree with AU_Tiger: "good" and "bad" derailers can both shift well or poorly, and there are more important considerations for a bike. The fundamentals like fit and whether you want suspension or disc brakes or...those are the critical things. Components can be changed over time, but the fundamentals like frame design cannot.

Both the Roam and Crosstrail (and DS, and others) use the SR Suntour NEX fork. The Roam and DS claim 63mm of travel, while the Crosstrail does claim only 55mm. I presume this is because there's additional "stuff" inside the lower stanchion for Specialized's "Brain technology" damping, which reduces the travel. I think it's the same basic fork...just different guts. I don't think the Specialized "Brain" fork has a lockout, so that's something to think about, or at least double-check as you shop.