If he is holding out for 300k, then there's no way he's going to Roma. Frankly, I don't believe he is holding out for that much, as it's about 50% higher than what Van Dijk is on, and Roma's interest would've been rebuffed before it even made the news. Is there a single center back on the planet making that type of money?
I don't think he's signed for Spurs because they don't really pay competitive wages. I believe the contract extensions they've offered him were more in the 130-150K range. If put on a 3-year contract, I think he is worth close to 200K. He might also be able to negotiate a signing on fee of 5 million pounds or so. I think it would be worth it for him to hold out for that if money is important, as it seems reasonable to think he could get that from someone like United, City, Barca, or Juventus.
I'm generally not a fan of signing older players, but center backs tend to have a little more career longevity than most other positions, and there's a real dearth of quality options out there right now, even for big money.