and in case you're interested in a long time period Rodinal test about lifetime:
For FP4+ I would personally recommend another developer than Rodinal but it depends for what kind of characteristics you're searching for. But the combination of fine grain and high accutance is a fraction which you can reach with the Rodinal APX100/Rollei Retro 100 combination. Another good Rodinal combo is Fomapan 100. If you like sharpness pronounced grain in architecture old look you can also go for the T200 (Creative 200) film from Foma with Rodinal.
Staying with the Ilford films PAN F is also a nice film combo with Rodinal.
To make the right high dilution of Rodinal you can use the 10ml plastic syrenges of the pharmacy and yes Rodinal is a one shot developer but that you can also read in it's instruction manual. Unfortunately not all developer times are correct in the sheet.