You are able to convert the following types of accounts: Traditional IRA, SEP IRA, and Roth 401K. These are available in the "choose a source" drop down. If there is not already a Roth IRA in the assets and liabilities section, it will prompt you to create a new one. If you already have the Roth IRA, it will show up in the destination list.
Additionally, if the account is owned by the spouse, then that Roth IRA would have to be owned by the spouse as well for it to show up in the destination list, otherwise it will also prompt you to create one for the spouse.