Simple question - I'm thinking about converting a regular IRA to a Roth IRA. Will I be allowed to offset the taxable gain on the conversion with some investment losses I took this year?

$3,000 of losses can be offset against your income, provided that you don't have capital gains that would cancel them out.

There is no capital gain treatment with an IRA ever. The increase in value that you recognize with your Roth conversion is ordinary income. As the previous poster noted up to $3,000 of net capital losses reduce your ordinary income - which includes the Roth conversion. Take losses if you must but it's not necessary to try to match them with Roth conversion income.

Thanks.