Maximum resolution on YouTube at present is 1920x1080. I'm sure you could upload a 4K file, but it would be down-rezzed.
Premiere Pro doesn't ship with an H.264 1080p preset for YouTube, but you could use the H.264 720p YouTube preset as a starting point and then increase the dimensions as well as the bit rate a tad. You'll have to do a little experimentation to find the bit rate that preserves the most quality after YouTube does its dance on your upload. YouTube no longer passes through anything--everything uploaded is reencoded--but there's a practical limit to which you can increase the bit rate before you start receiving diminishing returns for longer uploads.
My YT 1080p preset is something like Average Bit Rate 8Mbps/Maximum Bit Rate 10Mbps, but typically my videos don't go much over 5Mbps due to the content. Every video is different.
So how do people get 4K files to YouTube? They upload the RAW R3D file?
I'm saying that most people don't--and I'm not sure YT would accept any 4K file, much less an R3D file. You'd be uploading forever...
I'm confused: are you trying to post a finished video on YT or distribute raw footage?
OK. There you have it. Frankly, I don't see the point--it takes forever to buffer and I don't know about you, but I don't have a 4K monitor.
Why not try to upload an R3D file? YT is going to convert whatever you upload, anyway, so if that doesn't work you can always try an MP4.
I downloaded one of those. Here are the guts:
General Complete name : E:\Life_in_the_Garden_4k_resolution.mp4 Format : MPEG-4 Format profile : Base Media / Version 2 Codec ID : mp42 File size : 268 MiB Duration : 1mn 53s Overall bit rate : 19.8 Mbps Encoded date : UTC 2010-07-18 07:21:35 Tagged date : UTC 2010-07-18 07:21:35 gsst : 0 gstd : 113696 gssd : BADC207A5MH1316661840244974 gshh : o-o.preferred.iad09s10.v5.lscache4.c.youtube.com Video ID : 2 Format : AVC Format/Info : Advanced Video Codec Format profile : High@L5.1 Format settings, CABAC : No Format settings, ReFrames : 1 frame Format settings, GOP : M=1, N=60 Codec ID : avc1 Codec ID/Info : Advanced Video Coding Duration : 1mn 53s Bit rate : 19.7 Mbps Maximum bit rate : 60.3 Mbps Width : 4 096 pixels Height : 2 304 pixels Display aspect ratio : 16:9 Frame rate mode : Constant Frame rate : 23.976 fps Color space : YUV Chroma subsampling : 4:2:0 Bit depth : 8 bits Scan type : Progressive Bits/(Pixel*Frame) : 0.087 Stream size : 267 MiB (99%) Title : (C) 2007 Google Inc. v08.13.2007. Encoded date : UTC 2010-07-18 07:21:35 Tagged date : UTC 2010-07-18 07:21:37 Audio ID : 1 Format : AAC Format/Info : Advanced Audio Codec Format profile : LC Codec ID : 40 Duration : 1mn 53s Bit rate mode : Variable Bit rate : 119 Kbps Maximum bit rate : 178 Kbps Channel(s) : 2 channels Channel positions : Front: L R Sampling rate : 48.0 KHz Compression mode : Lossy Stream size : 1.62 MiB (1%) Title : (C) 2007 Google Inc. v08.13.2007. Encoded date : UTC 2010-07-18 07:21:35 Tagged date : UTC 2010-07-18 07:21:37