I am able to use human voice "ooh" and "ahh" sounds in Rosegarden using the FluidR3_GM2-2.sf2 soundfont. This (for me) is under Arch 64 bit as a virualbox guest using Timidity as the midi daemon under ALSA. All of this is open source and the soundfont is free with no royalties.
This will satisfy the part of your question "instead of playing the normal piano tone, it will play the same tone with human voice". I'm not clear if this is what you are looking for or if you are specifically looking for "do-re-mi".
Arch Timidity Wiki page: https://wiki.archlinux.org/index.php/timidity
The Arch Timidity wiki page details how to setup Timidity as a daemon / user service and should be distribution neutral (though some distributions organize /etc differently than others). More straight forward than the way I used to use Jack. The first time you use Rosegarden you might need to specify use of timidity through Studio...Manage MIDI Devices.