There are times I create a roleplay, people join in flocks. Others I get literally one person committed to joining. In cases of getting only one or two people, yet it's a Roleplay you've been urging to make, how do you react to this frustration?

Roll with the people you've got and recruit your heart out. Open an interest check and make sure it's always on the first page. Link to your RP in your sig. Ask the few who joined to do the same.

Additionally, depending on the setup of your RP, you might not need a ton of people for the RP to be stable and keep running. Plus, once you've got it started, who's to say more people won't want to jump on board?

Of course, whether or not newcomers can join beyond that point depends on the setup of the RP and you're GMing style, but yeah, my point is, you don't have to worry about numbers so much. If you only get a few people and advertising/recruiting isn't working for you, then just focus on making the RP work with the members you have. Sometimes a tight-knit group of 3-4 players is a lot better than a larger group within which half the players will lose interest and leave, forcing you to work around the problems caused by their sudden absences.

Roleplay it anyway. It just means things will go at a much faster pace, and each character will have a greater narrative force.

Sometimes it might just take a bit of advertising and letting people know that you're still accepting. A lot of the time (especially if there's a lot of posts made IC or OOC), people become intimidated to even just stick around to ask if you're still open. Write it in big letters you're still accepting, create a small summary of events every so often if you can so people can catch up, put the usual 'ignore post count/always accepting' sign in the title, etc... Basically, make it very user-friendly. :

But like the people said above, sometimes having a few just works better for some RPs.

Oh, and keep the plot in such a way that necomers can still easily join-up at several points (that or start a que).

Sometimes a small group is better than a larger more diverse group. It's easier to brainstorm and those people could always take on multiple characters as well.