Are they able to meet it if they so choose?
Absolutely, anyone who's a US citizen should be able to procure the appropriate things needed if they want to.
Also, if one put the system in place close to an election it could practically bar a high number of earlier eligible voters from making their voice heard. That would normally be seen as a bad thing.
Do everyone in the US that gets to vote have social security number?
Couldn't they use that to make the electoral rolls, and then have only an ID/drivers license to make sure that it is the correct person?
The overwhelming majority do. Issuing of SSNs typically happens at birth now and has been that way since that way for several decades.
It's also a requirement for anyone who's ever worked, banked, or applied for any sort of benefits.
So when you chisel it down to who that would actually impact (with regards to US citizens)
- Citizens who were born abroad to American parents, before the 1980's, and who've never worked, opened a bank account, applied for credit, applied for benefits. Or religious objectors like some sects of Amish who wish to remain detached from modern society for religious reasons.
And even then, there's alternative procedures available to that vanishingly thin minority of people in the form of things like a DS-11 (which will allow the aforementioned to get a passport, and thereby, prove US citizenship)
Just for kicks, I asked Anthropic what the current estimates were for people who fit that extremely narrow criteria, the estimate was 100,000-200,000 people, (80,000 of which are Amish).
To put that in perspective, there are more non-citizens with Social Security numbers than there are citizens without one (by a multiple of 10)
Which goes to your other question. The reason they can't just automatically add everyone with an SSN to the voter rolls is because non-citizens can get an SSN issued (for certain work authorizations and foreign exchange programs)